Ventilator-initiated prompt regarding auto-peep detection during ventilation of non-triggering patient

ABSTRACT

This disclosure describes systems and methods for monitoring and evaluating ventilatory parameters, analyzing those parameters and providing useful notifications and recommendations to clinicians. That is, modern ventilators monitor, evaluate, and graphically represent a myriad of ventilatory parameters. However, many clinicians may not easily identify or recognize data patterns and correlations indicative of certain patient conditions, changes in patient condition, and/or effectiveness of ventilatory treatment. Further, clinicians may not readily determine appropriate ventilatory adjustments that may address certain patient conditions and/or the effectiveness of ventilatory treatment. Specifically, clinicians may not readily detect or recognize the presence of Auto-PEEP during volume ventilation of a non-triggering patient. According to embodiments, a ventilator may be configured to monitor and evaluate diverse ventilatory parameters to detect Auto-PEEP and may issue suitable notifications and recommendations to the clinician when Auto-PEEP is implicated. The suitable notifications and recommendations may further be provided in a hierarchical format.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/775,565 (now U.S. Pat. No. 8,638,200), entitled“VENTILATOR-INITIATED PROMPT REGARDING AUTO-PEEP DETECTION DURING VOLUMEVENTILATION OF NON-TRIGGERING PATIENT,” filed on May 7, 2010, the entiredisclosure of which is hereby incorporated herein by reference.

INTRODUCTION

A ventilator is a device that mechanically helps patients breathe byreplacing some or all of the muscular effort required to inflate anddeflate the lungs. In recent years, there has been an accelerated trendtowards an integrated clinical environment. That is, medical devices arebecoming increasingly integrated with communication, computing, andcontrol technologies. As a result, modern ventilatory equipment hasbecome increasingly complex, providing for detection and evaluation of amyriad of ventilatory parameters. However, due to the shear magnitude ofavailable ventilatory data, many clinicians may not readily assess andevaluate the diverse ventilatory data to detect certain patientconditions and/or changes in patient condition. For example, Auto-PEEPis a dangerous condition associated with gas-trapping in the lungs thatmay be implicated by slight changes in a variety of differentparameters. Although quite serious, Auto-PEEP is difficult to diagnosebecause it is not easily recognized or detected by clinicians during theventilation of a patient.

Indeed, clinicians and patients may greatly benefit from ventilatornotifications when evaluation of various ventilatory data is indicativeof certain patient conditions, changes in patient condition,effectiveness of ventilatory therapy, or otherwise.

VENTILATOR-INITIATED PROMPT REGARDING AUTO-PEEP DETECTION DURING VOLUMEVENTILATION OF NON-TRIGGERING PATIENT

This disclosure describes systems and methods for monitoring andevaluating ventilatory parameters, analyzing ventilatory data associatedwith those parameters, and providing useful notifications and/orrecommendations to clinicians. Modern ventilators monitor, evaluate, andgraphically represent a myriad of ventilatory parameters. However, manyclinicians may not easily identify or recognize data patterns andcorrelations indicative of certain patient conditions, changes inpatient condition, and/or effectiveness of ventilatory treatment.Further, clinicians may not readily determine appropriate ventilatoryadjustments that may address certain patient conditions and/or theeffectiveness of ventilatory treatment. Specifically, clinicians may notreadily detect or recognize the presence of Auto-PEEP during volumeventilation of a non-triggering patient. According to embodiments, aventilator may be configured to monitor and evaluate diverse ventilatoryparameters to detect Auto-PEEP and may issue suitable notifications andrecommendations to the clinician when Auto-PEEP is implicated. Thesuitable notifications and recommendations may further be provided in ahierarchical format such that the clinician may selectively accesssummarized and/or detailed information regarding the presence ofAuto-PEEP. In more automated systems, recommendations may beautomatically implemented.

According to embodiments, a ventilator-implemented method for detectingAuto-PEEP during volume ventilation of a non-triggering patient isprovided. The methods include collecting data associated withventilatory parameters and processing the collected ventilatoryparameter data, wherein processing the collected ventilatory parameterdata includes deriving ventilatory parameter data from the collectedventilatory parameter data. The methods also include analyzing theprocessed ventilatory parameter data, which includes receiving one ormore predetermined thresholds associated with the processed ventilatoryparameter data, and detecting whether the processed ventilatoryparameter data breaches the one or more predetermined thresholds.Further, the methods include determining that Auto-PEEP is implicatedupon detecting that the processed ventilatory data breaches the one ormore predetermined thresholds. The methods further include issuing asmart prompt when Auto-PEEP is implicated.

According to further embodiments, a ventilatory system for issuing asmart prompt when Auto-PEEP is implicated during volume ventilation of anon-triggering patient is provided. Methods implemented by theventilatory system include detecting that Auto-PEEP is implicated forthe non-triggering patient and identifying processed ventilatoryparameter data that implicated Auto-PEEP. An appropriate notificationmessage and an appropriate recommendation message may be determined andeither or both of the appropriate notification message and theappropriate recommendation message may be displayed.

According to further embodiments, a ventilator graphical user interfacefor displaying one or more smart prompts corresponding to a detectedpatient condition is provided. The graphical user interface includes atleast one window associated with the graphical user interface and one ormore elements within the at least one window comprising at least onesmart prompt element for communicating information regarding thedetected patient condition.

These and various other features as well as advantages whichcharacterize the systems and methods described herein will be apparentfrom a reading of the following detailed description and a review of theassociated drawings. Additional features are set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the technology. Thebenefits and features of the technology will be realized and attained bythe structure particularly pointed out in the written description andclaims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawing figures, which form a part of this application,are illustrative of described technology and are not meant to limit thescope of the claims in any manner, which scope shall be based on theclaims appended hereto.

FIG. 1 is a diagram illustrating an embodiment of an exemplaryventilator connected to a human patient.

FIG. 2 is a block-diagram illustrating an embodiment of a ventilatorysystem for monitoring and evaluating ventilatory parameters associatedwith Auto-PEEP.

FIG. 3 is a flow chart illustrating an embodiment of a method fordetecting an implication of Auto-PEEP.

FIG. 4 is a flow chart illustrating an embodiment of a method forissuing a smart prompt upon detecting an implication of Auto-PEEP.

FIG. 5 is an illustration of an embodiment of a graphical user interfacedisplaying a smart prompt having a notification message.

FIG. 6 is an illustration of an embodiment of a graphical user interfacedisplaying an expanded smart prompt having a notification message andone or more recommendation messages.

DETAILED DESCRIPTION

Although the techniques introduced above and discussed in detail belowmay be implemented for a variety of medical devices, the presentdisclosure will discuss the implementation of these techniques for usein a mechanical ventilator system. The reader will understand that thetechnology described in the context of a ventilator system could beadapted for use with other therapeutic equipment for alerting andadvising clinicians regarding detected patient conditions.

This disclosure describes systems and methods for monitoring andevaluating ventilatory parameters, analyzing ventilatory data associatedwith those parameters, and providing useful notifications and/orrecommendations to clinicians. Modern ventilators monitor, evaluate, andgraphically represent a myriad of ventilatory parameters. However, manyclinicians may not easily identify or recognize data patterns andcorrelations indicative of certain patient conditions, changes inpatient condition, and/or effectiveness of ventilatory treatment.Further, clinicians may not readily determine appropriate ventilatoryadjustments that may address certain patient conditions and/or theeffectiveness of ventilatory treatment. Specifically, clinicians may notreadily detect or recognize the presence of Auto-PEEP during volumeventilation of a non-triggering patient. According to embodiments, aventilator may be configured to monitor and evaluate diverse ventilatoryparameters to detect Auto-PEEP and may issue suitable notifications andrecommendations to the clinician when Auto-PEEP is implicated. Thesuitable notifications and recommendations may further be provided in ahierarchical format such that the clinician may selectively accesssummarized and/or detailed information regarding the presence ofAuto-PEEP. In more automated systems, recommendations may beautomatically implemented.

Ventilator System

FIG. 1 is a diagram illustrating an embodiment of an exemplaryventilator 100 connected to a human patient 150. Ventilator 100 includesa pneumatic system 102 (also referred to as a pressure generating system102) for circulating breathing gases to and from patient 150 via theventilation tubing system 130, which couples the patient to thepneumatic system via an invasive (e.g., endotracheal tube, as shown) ora non-invasive (e.g., nasal mask) patient interface.

Ventilation tubing system 130 may be a two-limb (shown) or a one-limbcircuit for carrying gases to and from the patient 150. In a two-limbembodiment, a fitting, typically referred to as a “wye-fitting” 170, maybe provided to couple a patient interface 180 (as shown, an endotrachealtube) to an inspiratory limb 132 and an expiratory limb 134 of theventilation tubing system 130.

Pneumatic system 102 may be configured in a variety of ways. In thepresent example, system 102 includes an expiratory module 108 coupledwith the expiratory limb 134 and an inspiratory module 104 coupled withthe inspiratory limb 132. Compressor 106 or other source(s) ofpressurized gases (e.g., air, oxygen, and/or helium) is coupled withinspiratory module 104 to provide a gas source for ventilatory supportvia inspiratory limb 132.

The pneumatic system 102 may include a variety of other components,including mixing modules, valves, sensors, tubing, accumulators,filters, etc. Controller 110 is operatively coupled with pneumaticsystem 102, signal measurement and acquisition systems, and an operatorinterface 120 that may enable an operator to interact with theventilator 100 (e.g., change ventilator settings, select operationalmodes, view monitored parameters, etc.). Controller 110 may includememory 112, one or more processors 116, storage 114, and/or othercomponents of the type commonly found in command and control computingdevices. In the depicted example, operator interface 120 includes adisplay 122 that may be touch-sensitive and/or voice-activated, enablingthe display to serve both as an input and output device.

The memory 112 includes non-transitory, computer-readable storage mediathat stores software that is executed by the processor 116 and whichcontrols the operation of the ventilator 100. In an embodiment, thememory 112 includes one or more solid-state storage devices such asflash memory chips. In an alternative embodiment, the memory 112 may bemass storage connected to the processor 116 through a mass storagecontroller (not shown) and a communications bus (not shown). Althoughthe description of computer-readable media contained herein refers to asolid-state storage, it should be appreciated by those skilled in theart that computer-readable storage media can be any available media thatcan be accessed by the processor 116. That is, computer-readable storagemedia includes non-transitory, volatile and non-volatile, removable andnon-removable media implemented in any method or technology for storageof information such as computer-readable instructions, data structures,program modules or other data. For example, computer-readable storagemedia includes RAM, ROM, EPROM, EEPROM, flash memory or other solidstate memory technology, CD-ROM, DVD, or other optical storage, magneticcassettes, magnetic tape, magnetic disk storage or other magneticstorage devices, or any other medium which can be used to store thedesired information and which can be accessed by the computer.

Communication between components of the ventilatory system or betweenthe ventilatory system and other therapeutic equipment and/or remotemonitoring systems may be conducted over a distributed network, asdescribed further herein, via wired or wireless means. Further, thepresent methods may be configured as a presentation layer built over theTCP/IP protocol. TCP/IP stands for “Transmission ControlProtocol/Internet Protocol” and provides a basic communication languagefor many local networks (such as intra- or extranets) and is the primarycommunication language for the Internet. Specifically, TCP/IP is abi-layer protocol that allows for the transmission of data over anetwork. The higher layer, or TCP layer, divides a message into smallerpackets, which are reassembled by a receiving TCP layer into theoriginal message. The lower layer, or IP layer, handles addressing androuting of packets so that they are properly received at a destination.

Ventilator Components

FIG. 2 is a block-diagram illustrating an embodiment of a ventilatorysystem for monitoring and evaluating ventilatory parameters associatedwith Auto-PEEP.

Ventilatory system 200 includes ventilator 202 with its various modulesand components. That is, ventilator 202 may further include, inter alia,memory 208, one or more processors 206, user interface 210, andventilation module 212 (which may further include an inspiration module214 and an expiration module 216). Memory 208 is defined as describedabove for memory 112. Similarly, the one or more processors 206 aredefined as described above for one or more processors 116. Processors206 may further be configured with a clock whereby elapsed time may bemonitored by the system 200.

The ventilatory system 200 may also include a display module 204communicatively coupled to ventilator 202. Display module 204 providesvarious input screens, for receiving clinician input, and variousdisplay screens, for presenting useful information to the clinician. Thedisplay module 204 is configured to communicate with user interface 210and may include a graphical user interface (GUI). The GUI may be aninteractive display, e.g., a touch-sensitive screen or otherwise, andmay provide various windows and elements for receiving input andinterface command operations. Alternatively, the GUI may provide othersuitable means of communication with the ventilator 202, for instance bya wheel, keyboard, mouse, or other suitable interactive device. Thus,user interface 210 may accept commands and input through display module204. Display module 204 may also provide useful information in the formof various ventilatory data regarding the physical condition of apatient and/or a prescribed respiratory treatment. The usefulinformation may be derived by the ventilator 202, based on datacollected by a data processing module 222, and the useful informationmay be displayed to the clinician in the form of graphs, waverepresentations, pie graphs, or other suitable forms of graphic display.For example, one or more smart prompts may be displayed on the GUIand/or display module 204 upon detection of an implication of Auto-PEEPby the ventilator. Additionally or alternatively, one or more smartprompts may be communicated to a remote monitoring system coupled viaany suitable means to the ventilatory system 200.

Equation of Motion

Ventilation module 212 may oversee ventilation of a patient according toprescribed ventilatory settings. By way of general overview, the basicelements impacting ventilation may be described by the followingventilatory equation (also known as the Equation of Motion):P _(m) +P _(v) =V _(T) /C+R*FHere, P_(m) is a measure of muscular effort that is equivalent to thepressure generated by the muscles of a patient. If the patient's musclesare inactive, the P_(m) is equivalent to 0 cm H₂O. During inspiration,P_(v) represents the positive pressure delivered by a ventilator(generally in cm H₂O). V_(T) represents the tidal volume delivered, Crefers to the respiratory compliance, R represents the respiratoryresistance, and F represents the gas flow during inspiration (generallyin liters per min (L/m)). Alternatively, during expiration, the Equationof Motion may be represented as:P _(a) +P _(t) =V _(TE) /C+R*FHere, P_(a) represents the positive pressure existing in the lungs(generally in cm H₂O), P_(t) represents the transairway pressure, V_(TE)represents the tidal volume exhaled, C refers to the respiratorycompliance, R represents the respiratory resistance, and F representsthe gas flow during expiration (generally in liters per min (L/m)).Pressure

For positive pressure ventilation, pressure at the upper airway opening(e.g., in the patient's mouth) is positive relative to the pressure atthe body's surface (i.e., relative to the ambient atmospheric pressureto which the patient's body surface is exposed, about 0 cm H₂O). Assuch, when P_(v) is zero, i.e., no ventilatory pressure is beingdelivered, the upper airway opening pressure will be equal to theambient pressure (i.e., about 0 cm H₂O). However, when ventilatorypressure is applied, a pressure gradient is created that allows gases toflow into the airway and ultimately into the lungs of a patient duringinspiration (or, inhalation).

According to embodiments, additional pressure measurements may beobtained and evaluated. For example, transairway pressure, P_(t), whichrefers to the pressure differential or gradient between the upper airwayopening and the alveoli, may also be determined. P_(t) may berepresented mathematically as:P _(t) =P _(awo) −P _(a)Where P_(awo) refers to the pressure in the upper airway opening, ormouth, and P_(a) refers to the pressure within the alveolar space, orthe lungs (as described above). P_(t) may also be represented asfollows:P _(t) =F*RWhere F refers to flow and R refers to respiratory resistance, asdescribed below,

Additionally, lung pressure or alveolar pressure, P_(a), may be measuredor derived. For example, P_(a) may be measured via a distal pressuretransducer or other sensor near the lungs and/or the diaphragm.Alternatively, P_(a) may be estimated by measuring the plateau pressure,P_(Plat), via a proximal pressure transducer or other sensor at or nearthe airway opening. Plateau pressure, P_(Plat), refers to a slightplateau in pressure that is observed at the end of inspiration wheninspiration is held for a period of time, sometimes referred to as aninspiratory hold or pause maneuver, or a breath-hold maneuver. That is,when inspiration is held, pressure inside the alveoli and mouth areequal (i.e., no gas flow). However, as a result of muscular relaxationand elastance of the lungs during the hold period, forces are exerted onthe inflated lungs that create a positive pressure. This positivepressure is observed as a plateau in the pressure waveform that isslightly below the peak inspiratory pressure, P_(Peak), prior toinitiation of expiration. As may be appreciated, for accuratemeasurement of P_(Plat), the patient should be sedated ornon-spontaneous (as muscular effort during the inspiratory pause mayskew the pressure measurement). Upon determining P_(Plat) based on thepressure waveform or otherwise, P_(Plat) may be used as an estimate ofP_(a) (alveolar pressure).

Flow and Volume

Volume refers to the amount of gas delivered to a patient's lungs,usually in liters (L). Flow refers to a rate of change in volume overtime (F=ΔV/Δt). Flow is generally expressed in liters per minute (L/m orlpm) and, depending on whether gases are flowing into or out of thelungs, flow may be referred to as inspiratory flow or expiratory flow,respectively. According to embodiments, the ventilator may control therate of delivery of gases to the patient, i.e., inspiratory flow, andmay control the rate of release of gases from the patient, i.e.,expiratory flow.

As may be appreciated, volume and flow are closely related. That is,where flow is known or regulated, volume may be derived based on elapsedtimes Indeed, volume may be derived by integrating the flow waveform.According to embodiments, a tidal volume, V_(T), may be delivered uponreaching a set inspiratory time (T_(I)) at set inspiratory flow.Alternatively, set V_(T) and set inspiratory flow may determine theamount of time required for inspiration, i.e., T_(I).

Respiratory Compliance

Additional ventilatory parameters that may be measured and/or derivedmay include respiratory compliance and respiratory resistance, whichrefer to the load against which the patient and/or the ventilator mustwork to deliver gases to the lungs. Respiratory compliance may beinterchangeably referred to herein as compliance. Generally, compliancerefers to a relative ease with which something distends and is theinverse of elastance, which refers to the tendency of something toreturn to its original form after being deformed. As related toventilation, compliance refers to the lung volume achieved for a givenamount of delivered pressure (C=ΔV/ΔP). Increased compliance may bedetected when the ventilator measures an increased volume relative tothe given amount of delivered pressure. Some lung diseases (e.g., acuterespiratory distress syndrome (ARDS)) may decrease compliance and, thus,require increased pressure to inflate the lungs. Alternatively, otherlung diseases may increase compliance, e.g., emphysema, and may requireless pressure to inflate the lungs.

Additionally or alternatively, static compliance and dynamic compliancemay be calculated. Static compliance, C_(s), represents complianceimpacted by elastic recoil at zero flow (e.g., of the chest wall,patient circuit, and alveoli). As elastic recoil of the chest wall andpatient circuit may remain relatively constant, static compliance maygenerally represent compliance as affected by elastic recoil of thealveoli. As described above, P_(Plat) refers to a slight plateau inpressure that is observed after relaxation of pleural muscles andelastic recoil, i.e., representing pressure delivered to overcomeelastic forces. As such, P_(Plat) provides a basis for estimating C_(s)as follows:C _(S) =V _(T)/(P _(Plat)−EEP)Where V_(T) refers to tidal volume, P_(Plat) refers to plateau pressure,and EEP refers to end-expiratory pressure, or baseline pressure(including PEEP and/or Auto-PEEP), as discussed below. Note that propercalculation of C_(S) depends on accurate measurement of V_(T) andP_(Plat).

Dynamic compliance, C_(D), is measured during airflow and, as such, isimpacted by both elastic recoil and airway resistance. Peak inspiratorypressure, P_(Peak), which represents the highest pressure measuredduring inspiration, i.e., pressure delivered to overcome both elasticand resistive forces to inflate the lungs, is used to calculate C_(D) asfollows:C _(D) =V _(T)/(P _(Peak)−EEP)Where V_(T) refers to tidal volume, P_(Peak) refers to peak inspiratorypressure, and EEP refers to end-expiratory pressure. According toembodiments, ventilatory data may be more readily available for trendingcompliance of non-triggering patients than of triggering patients.Respiratory Resistance

Respiratory resistance refers to frictional forces that resist airflow,e.g., due to synthetic structures (e.g., endotracheal tube, expiratoryvalve, etc.), anatomical structures (e.g., bronchial tree, esophagus,etc.), or viscous tissues of the lungs and adjacent organs. Respiratoryresistance may be interchangeably referred to herein as resistance.Resistance is highly dependant on the diameter of the airway. That is, alarger airway diameter entails less resistance and a higher concomitantflow. Alternatively, a smaller airway diameter entails higher resistanceand a lower concomitant flow. In fact, decreasing the diameter of theairway results in an exponential increase in resistance (e.g., two-timesreduction of diameter increases resistance by sixteen times). As may beappreciated, resistance may also increase due to a restriction of theairway that is the result of, inter alia, increased secretions,bronchial edema, mucous plugs, brochospasm, and/or kinking of thepatient interface (e.g., invasive endotracheal or tracheostomy tubes).

Airway resistance may further be represented mathematically as:R−P _(t) /FWhere P_(t) refers to the transairway pressure and F refers to the flow.That is, P_(t) refers to the pressure necessary to overcome resistiveforces of the airway. Resistance may be expressed in centimeters ofwater per liter per second (i.e., cm H₂O/L/s).Pulmonary Time Constant

As discussed above, compliance refers to the lung volume achieved for agiven amount of delivered pressure (C=ΔV/ΔP). That is, stateddifferently, volume delivered is equivalent to the compliance multipliedby the delivered pressure (ΔV=C*ΔP). However, as the lungs are notperfectly elastic, a period of time is needed to deliver the volume ΔVat pressure ΔP. A pulmonary time constant, τ, may represent a timenecessary to inflate or exhale a given percentage of the volume atdelivered pressure ΔP. The pulmonary time constant, τ, may be calculatedby multiplying the respiratory resistance by the respiratory compliance(τ=R*C) for a given patient and τ is generally represented in seconds,s. The pulmonary time constant associated with exhalation of the givenpercentage of volume may be termed an expiratory time constant and thepulmonary time constant associated with inhalation of the givenpercentage of volume may be termed an inspiratory time constant.

According to some embodiments, when expiratory resistance data isavailable, the pulmonary time constant may be calculated by multiplyingexpiratory resistance by compliance. According to alternativeembodiments, the pulmonary time constant may be calculated based oninspiratory resistance and compliance. According to further embodiments,the expiratory time, T_(E), should be equal to or greater than three (3)pulmonary time constants to ensure adequate exhalation. That is, for atriggering patient, T_(E) (e.g., determined by trending T_(E) orotherwise) should be equal to or greater than 3 pulmonary timeconstants. For a non-triggering patient, set RR should yield a T_(E)that is equal to or greater than 3 pulmonary time constants.

Normal Resistance and Compliance

According to embodiments, normal respiratory resistance and compliancemay be determined based on a patient's predicted body weight (PBW) (orideal body weight (IBW)). That is, according to a standardized protocolor otherwise, patient data may be compiled such that normal respiratoryresistance and compliance values and/or ranges of values may bedetermined and provided to the ventilatory system. That is, amanufacturer, clinical facility, clinician, or otherwise, may configurethe ventilator with normal respiratory resistance and compliance valuesand/or ranges of values based on PBWs (or IBWs) of a patient population.Thereafter, during ventilation of a particular patient, respiratoryresistance and compliance data may be trended for the patient andcompared to normal values and/or ranges of values based on theparticular patient's PBW (or IBW). According to embodiments, theventilator may give an indication to the clinician regarding whether thetrended respiratory resistance and compliance data of the particularpatient falls into normal ranges. According to some embodiments, datamay be more readily available for trending resistance and compliance fornon-triggering patients than for triggering patients.

According to further embodiments, a predicted T_(E) may be determinedbased on a patient's PBW (or IBW). That is, according to a standardizedprotocol or otherwise, patient population data may be compiled such thatpredicted T_(E) values and/or ranges of values may be determined basedon PBWs (or IBWs) of the patient population and provided to theventilatory system. Actual (or trended) T_(E) for a particular patientmay then be compared to the predicted T_(E). As noted previously,increased resistance and/or compliance may result in an actual T_(E)that is longer than predicted T_(E). However, when actual T_(E) isconsistent with predicted T_(E), this may indicate that resistance andcompliance for the particular patient fall into normal ranges.

According to further embodiments, a normal pulmonary time constant, τ,may be determined based on a patient's PBW (or IBW). That is, accordingto a standardized protocol or otherwise, patient population data may becompiled such that normal τ values and/or ranges of values may bedetermined based on PBWs (or IBWs) of the patient population andprovided to the ventilatory system. A calculated τ may be determined fora particular patient by multiplying resistance by compliance (asdescribed above, resistance and compliance data may be more readilyavailable for a non-triggering patient). As the product of resistanceand compliance results in τ, increased resistance and/or compliance mayresult in an elevated τ value. However, when the calculated τ value forthe particular patient is consistent with the normal τ value, this mayindicate that the resistance and compliance of the particular patientfall into normal ranges.

Obstructive Component

Some patients may exhibit an obstructive component due to variousconditions and diseases, e.g., COPD, ARDS, etc. That is, an obstructivecomponent may be associated with patients that exhibit chronic elevatedresistance due to constricted airways, alveolar collapse, etc. Accordingto some embodiments, patients having these conditions may also exhibitelevated compliance. According to embodiments, determination ofAuto-PEEP and/or determination of appropriate recommendations formitigating Auto-PEEP may vary for patients exhibiting an obstructivecomponent. As such, the ventilator may be configured to detect anobstructive component and/or may receive an indication from theclinician regarding whether the patient has been diagnosed with anobstructive disease. According to embodiments, when an obstructivecomponent is detected, the ventilator may be configured with adjustedsensitivity to Auto-PEEP and/or may be configured to alter one or morerecommendations for mitigating Auto-PEEP based on the detection of anobstructive component.

According to embodiments, normal respiratory resistance and compliancemay be determined based on a patient's PBW (or IBW), as described above.During ventilation of a specific patient, respiratory resistance andcompliance data may be trended for the patient and compared to normalvalues and/or ranges of values based on the specific patient's PBW (orIBW). According to embodiments, the ventilator may alert the clinicianwhen the trended respiratory resistance and/or compliance data of theparticular patient fall outside normal ranges. For example, whenresistance data for a particular patient falls outside normal ranges,the ventilator may alert the clinician that the patient may have anobstructive component.

According to further embodiments, predicted T_(E) may be determinedbased on a patient's PBW (or IBW), as described above. Actual (ortrended) T_(E) for a particular patient may then be compared to thepredicted T_(E). When actual T_(E) is greater than predicted T_(E), thismay indicate that resistance and/or compliance of the particular patientfalls outside normal ranges. When compliance has not changed, anelevated T_(E) may be attributable to resistance and the ventilator mayalert the clinician that the patient may have an obstructive component.

According to further embodiments, a normal pulmonary time constant, τ,may be determined based on a patient's PBW (or IBW), as described above.A calculated τ may be determined for a particular patient by multiplyingresistance by compliance. When the calculated τ value is greater thanthe normal τ value, this may indicate that resistance and/or compliancefor the particular patient fall outside normal ranges. When compliancehas not changed, the elevated T_(E) may be attributable to resistanceand the ventilator may alert the clinician that the patient may have anobstructive component.

According to further embodiments, a clinician may input a patientdiagnosis, e.g., COPD or emphysema. The ventilator may associate thepatient diagnosis with certain lung and airway characteristics. Forexample, if the ventilator receives a patient diagnosis of COPD, theventilator may associate this patient diagnosis with elevatedresistance. Further, the ventilator may associate COPD with anobstructive component. Alternatively, if the ventilator receives apatient diagnosis of emphysema, the ventilator may associate thispatient diagnosis with elevated compliance.

Inspiration

Ventilation module 212 may further include an inspiration module 214configured to deliver gases to the patient according to prescribedventilatory settings. Specifically, inspiration module 214 maycorrespond to the inspiratory module 104 or may be otherwise coupled tosource(s) of pressurized gases (e.g., air, oxygen, and/or helium), andmay deliver gases to the patient. Inspiration module 214 may beconfigured to provide ventilation according to various ventilatorymodes, e.g., via volume-targeted, pressure-targeted, or via any othersuitable mode of ventilation.

Volume ventilation refers to various forms of volume-targetedventilation that regulate volume delivery to the patient. Differentmodes of volume ventilation are available depending on the specificimplementation of volume regulation. For example, for volume-cycledventilation, an end of inspiration is determined based on monitoring thevolume delivered to the patient. Volume ventilation may includevolume-control (VC), volume-assist, or volume assist/controlventilation. Volume ventilation may be accomplished by setting a targetvolume, or prescribed tidal volume, V_(T), for delivery to the patient.According to embodiments, prescribed V_(T) and inspiratory time (T_(I))may be set during ventilation start-up, based on the patient's PBW (orIBW). In this case, flow will be dependent on the prescribed V_(T) andset T_(I). Alternatively, prescribed V_(T) and flow may be set and T_(I)may result. According to some embodiments, a predicted T_(E) may bedetermined based on normal respiratory and compliance values or valueranges based on the patient's PBW (or IBW). Additionally, a respiratoryrate (RR) setting, generally in breaths/min, may be determined andconfigured. For a non-triggering patient, the RR will control the timingfor each inspiration. For a triggering patient, the RR setting willapply if the patient stops triggering for some reason and/or thepatient's triggered RR drops below a threshold level.

According to embodiments, during volume ventilation, as volume and floware regulated by the ventilator, delivered V_(T), flow waveforms (orflow traces), and volume waveforms may be constant and may not beaffected by variations in lung or airway characteristics (e.g.,respiratory compliance and/or respiratory resistance). Alternatively,pressure readings may fluctuate based on lung or airway characteristics.According to some embodiments, the ventilator may control theinspiratory flow and then derive volume based on the inspiratory flowand elapsed time. For volume-cycled ventilation, when the derived volumeis equal to the prescribed V_(T), the ventilator may initiateexpiration.

According to alternative embodiments, the inspiration module 214 mayprovide ventilation via a form of pressure ventilation.Pressure-targeted modes of ventilation may be provided by regulating thepressure delivered to the patient in various ways. For example, duringpressure-cycled ventilation, an end of inspiration is determined basedon monitoring the pressure delivered to the patient. Pressureventilation may include pressure-support ventilation (PSV) orpressure-control ventilation (PCV), for example. Pressure ventilationmay also include various forms of bi-level (BL) pressure ventilation,i.e., pressure ventilation in which the inspiratory positive airwaypressure (IPAP) is higher than the expiratory positive airway pressure(EPAP). Specifically, pressure ventilation may be accomplished bysetting a target or prescribed pressure for delivery to the patient. Asfor volume ventilation, predicted T_(I) may be determined based onnormal respiratory and compliance values and on the patient's PBW (orIBW). According to some embodiments, a predicted T_(E) may be determinedbased on normal respiratory and compliance values and based on thepatient's PBW (or IBW). A respiratory rate (RR) setting may also bedetermined and configured. For a non-triggering patient, the RR willcontrol the timing for each inspiration. For a triggering patient, theRR setting will apply if the patient stops triggering for some reasonand/or patient triggering drops below a threshold RR level.

According to embodiments, during pressure ventilation, the ventilatormay maintain the same pressure waveform at the mouth, P_(awo),regardless of variations in lung or airway characteristics, e.g.,respiratory compliance and/or respiratory resistance. However, thevolume and flow waveforms may fluctuate based on lung and airwaycharacteristics. As noted above, pressure delivered to the upper airwaycreates a pressure gradient that enables gases to flow into a patient'slungs. The pressure from which a ventilator initiates inspiration istermed the end-expiratory pressure KEEP) or “baseline” pressure. Thispressure may be atmospheric pressure (about 0 cm H₂O), also referred toas zero end-expiratory pressure (ZEEP). However, commonly, the baselinepressure may be positive, termed positive end-expiratory pressure(PEEP). Among other things, PEEP may promote higher oxygenationsaturation and/or may prevent alveolar collapse during expiration. Underpressure-cycled ventilation, upon delivering the prescribed pressure theventilator may initiate expiration.

According to still other embodiments, a combination of volume andpressure ventilation may be delivered to a patient, e.g.,volume-targeted-pressure-controlled (VC+) ventilation. In particular,VC+ ventilation may provide benefits of setting a target V_(T), whilealso allowing for monitoring variations in flow. As will be detailedfurther below, variations in flow may be indicative of various patientconditions.

Expiration

Ventilation module 212 may further include an expiration module 216configured to release gases from the patient's lungs according toprescribed ventilatory settings. Specifically, expiration module 216 maycorrespond to expiratory module 108 or may otherwise be associated withand/or controlling an expiratory valve for releasing gases from thepatient. By way of general overview, a ventilator may initiateexpiration based on lapse of an inspiratory time setting (T_(I)) orother cycling criteria set by the clinician or derived from ventilatorsettings (e.g., detecting delivery of prescribed V_(T) or prescribedpressure based on a reference trajectory). Upon initiating theexpiratory phase, expiration module 216 may allow the patient to exhaleby opening an expiratory valve. As such, expiration is passive, and thedirection of airflow, as described above, is governed by the pressuregradient between the patient's lungs (higher pressure) and the ambientsurface pressure (lower pressure). Although expiratory flow is passive,it may be regulated by the ventilator based on the size of theexpiratory valve opening.

Expiratory time (T_(E)) is the time from the end of inspiration untilthe patient triggers for a spontaneously breathing patient. For anon-triggering patient, it is the time from the end of inspiration untilthe next inspiration based on the set RR. In some cases, however, thetime required to return to the functional residual capacity (FRC) orresting capacity of the lungs is longer than provided by T_(E) (e.g.,because the patient triggers prior to fully exhaling or the RR is toohigh for a non-triggering patient). According to embodiments, variousventilatory settings may be adjusted to better match the time to reachFRC with the time available to reach FRC. For example, increasing flowwill shorten T_(I), thereby increasing the amount of time available toreach FRC. Alternatively, V_(T) may be decreased, resulting in less timerequired to reach FRC.

As may be further appreciated, at the point of transition betweeninspiration and expiration, the direction of airflow may abruptly changefrom flowing into the lungs to flowing out of the lungs or vice versadepending on the transition. Stated another way, inspiratory flow may bemeasurable in the ventilatory circuit until P_(Peak) is reached, atwhich point flow is zero. Thereafter, upon initiation of expiration,expiratory flow is measurable in the ventilatory circuit until thepressure gradient between the lungs and the body's surface reaches zero(again, resulting in zero flow). However, in some cases, as will bedescribed further herein, expiratory flow may still be positive, i.e.,measurable, at the end of expiration (termed positive end-expiratoryflow or positive EEF). In this case, positive EEF is an indication thatthe pressure gradient has not reached zero or, similarly, that thepatient has not completely exhaled. Although a single occurrence ofpremature inspiration may not warrant concern, repeated detection ofpositive EEF may be indicative of Auto-PEEP.

Ventilator Synchrony and Patient Triggering

According to some embodiments, the inspiration module 214 and/or theexpiration module 216 may be configured to synchronize ventilation witha spontaneously-breathing, or triggering, patient. That is, theventilator may be configured to detect patient effort and may initiate atransition from expiration to inspiration (or from inspiration toexpiration) in response. Triggering refers to the transition fromexpiration to inspiration in order to distinguish it from the transitionfrom inspiration to expiration (referred to as cycling). Ventilationsystems, depending on their mode of operation, may trigger and/or cycleautomatically, or in response to a detection of patient effort, or both.

Specifically, the ventilator may detect patient effort via apressure-monitoring method, a flow-monitoring method, direct or indirectmeasurement of nerve impulses, or any other suitable method. Sensingdevices may be either internal or distributed and may include anysuitable sensing device, as described further herein. In addition, thesensitivity of the ventilator to changes in pressure and/or flow may beadjusted such that the ventilator may properly detect the patienteffort, i.e., the lower the pressure or flow change setting the moresensitive the ventilator may be to patient triggering.

According to embodiments, a pressure-triggering method may involve theventilator monitoring the circuit pressure, as described above, anddetecting a slight drop in circuit pressure. The slight drop in circuitpressure may indicate that the patient's respiratory muscles, P_(m), arecreating a slight negative pressure gradient between the patient's lungsand the airway opening in an effort to inspire. The ventilator mayinterpret the slight drop in circuit pressure as patient effort and mayconsequently initiate inspiration by delivering respiratory gases.

Alternatively, the ventilator may detect a flow-triggered event.Specifically, the ventilator may monitor the circuit flow, as describedabove. If the ventilator detects a slight drop in flow duringexhalation, this may indicate, again, that the patient is attempting toinspire. In this case, the ventilator is detecting a drop in bias flow(or baseline flow) attributable to a slight redirection of gases intothe patient's lungs (in response to a slightly negative pressuregradient as discussed above). Bias flow refers to a constant flowexisting in the circuit during exhalation that enables the ventilator todetect expiratory flow changes and patient triggering. For example,while gases are generally flowing out of the patient's lungs duringexpiration, a drop in flow may occur as some gas is redirected and flowsinto the lungs in response to the slightly negative pressure gradientbetween the patient's lungs and the body's surface. Thus, when theventilator detects a slight drop in flow below the bias flow by apredetermined threshold amount (e.g., 2 L/min below bias flow), it mayinterpret the drop as a patient trigger and may consequently initiateinspiration by delivering respiratory gases.

Ventilator Sensory Devices

The ventilatory system 200 may also include one or more distributedsensors 218 communicatively coupled to ventilator 202. Distributedsensors 218 may communicate with various components of ventilator 202,e.g., ventilation module 212, internal sensors 220, data processingmodule 222, Auto-PEEP detection module 224, and any other suitablecomponents and/or modules. Distributed sensors 218 may detect changes inventilatory parameters indicative of Auto-PEEP, for example. Distributedsensors 218 may be placed in any suitable location, e.g., within theventilatory circuitry or other devices communicatively coupled to theventilator. For example, sensors may be affixed to the ventilatorytubing or may be imbedded in the tubing itself. According to someembodiments, sensors may be provided at or near the lungs (or diaphragm)for detecting a pressure in the lungs. Additionally or alternatively,sensors may be affixed or imbedded in or near wye-fitting 170 and/orpatient interface 180, as described above.

Distributed sensors 218 may further include pressure transducers thatmay detect changes in circuit pressure (e.g., electromechanicaltransducers including piezoelectric, variable capacitance, or straingauge). Distributed sensors 218 may further include various flowmetersfor detecting airflow (e.g., differential pressure pneumotachometers).For example, some flowmeters may use obstructions to create a pressuredecrease corresponding to the flow across the device (e.g., differentialpressure pneumotachometers) and other flowmeters may use turbines suchthat flow may be determined based on the rate of turbine rotation (e.g.,turbine flowmeters). Alternatively, sensors may utilize optical orultrasound techniques for measuring changes in ventilatory parameters. Apatient's blood parameters or concentrations of expired gases may alsobe monitored by sensors to detect physiological changes that may be usedas indicators to study physiological effects of ventilation, wherein theresults of such studies may be used for diagnostic or therapeuticpurposes. Indeed, any distributed sensory device useful for monitoringchanges in measurable parameters during ventilatory treatment may beemployed in accordance with embodiments described herein.

Ventilator 202 may further include one or more internal sensors 220.Similar to distributed sensors 218, internal sensors 220 may communicatewith various components of ventilator 202, e.g., ventilation module 212,internal sensors 220, data processing module 222, Auto-PEEP detectionmodule 224, and any other suitable components and/or modules. Internalsensors 220 may employ any suitable sensory or derivative technique formonitoring one or more parameters associated with the ventilation of apatient. However, the one or more internal sensors 220 may be placed inany suitable internal location, such as, within the ventilatorycircuitry or within components or modules of ventilator 202. Forexample, sensors may be coupled to the inspiratory and/or expiratorymodules for detecting changes in, for example, circuit pressure and/orflow. Specifically, internal sensors may include pressure transducersand flowmeters for measuring changes in circuit pressure and airflow.Additionally or alternatively, internal sensors may utilize optical orultrasound techniques for measuring changes in ventilatory parameters.For example, a patient's expired gases may be monitored by internalsensors to detect physiological changes indicative of the patient'scondition and/or treatment, for example. Indeed, internal sensors mayemploy any suitable mechanism for monitoring parameters of interest inaccordance with embodiments described herein.

As should be appreciated, with reference to the Equation of Motion,ventilatory parameters are highly interrelated and, according toembodiments, may be either directly or indirectly monitored. That is,parameters may be directly monitored by one or more sensors, asdescribed above, or may be indirectly monitored by derivation accordingto the Equation of Motion.

Ventilatory Data

Ventilator 202 may further include a data processing module 222. Asnoted above, distributed sensors 218 and internal sensors 220 maycollect data regarding various ventilatory parameters. A ventilatoryparameter refers to any factor, characteristic, or measurementassociated with the ventilation of a patient, whether monitored by theventilator or by any other device. Sensors may further transmitcollected data to the data processing module 222 and, according toembodiments, the data processing module may 222 be configured to collectdata regarding some ventilatory parameters, to derive data regardingother ventilatory parameters, and to graphically represent collected andderived data to the clinician and/or other modules of the ventilatorysystem. Some collected, derived, and/or graphically represented data maybe indicative of Auto-PEEP. For example, data regarding end-expiratoryflow (EEF), data regarding alveolar pressure P_(a) (e.g., via abreath-hold maneuver as described above), P_(Peak) data, P_(Plat) data,volume data, flow trace data, EEP data etc., may be collected, derived,and/or graphically represented by data processing module 222.

Flow Data

For example, according to embodiments, data processing module 222 may beconfigured to monitor inspiratory and expiratory flow. Flow may bemeasured by any appropriate, internal or distributed device or sensorwithin the ventilatory system. As described above, flowmeters may beemployed by the ventilatory system to detect circuit flow. However, anysuitable device either known or developed in the future may be used fordetecting airflow in the ventilatory circuit.

Data processing module 222 may be further configured to plot monitoredflow data graphically via any suitable means. For example, according toembodiments, flow data may be plotted versus time (flow waveform),versus volume (flow-volume loop), or versus any other suitable parameteras may be useful to a clinician. According to embodiments, flow may beplotted such that each breath may be independently identified. Further,flow may be plotted such that inspiratory flow and expiratory flow maybe independently identified, e.g., inspiratory flow may be representedin one color and expiratory flow may be represented in another color.According to additional embodiments, flow waveforms and flow-volumeloops, for example, may be represented alongside additional graphicalrepresentations, e.g., representations of volume, pressure, etc., suchthat clinicians may substantially simultaneously visualize a variety ofventilatory parameters associated with each breath.

As may be appreciated, flow decreases as resistance increases, making itmore difficult to pass gases into and out of the lungs (i.e.,F=P_(t)/R). For example, when a patient is intubated, i.e., havingeither an endotracheal or a tracheostomy tube in place, resistance maybe increased as a result of the smaller diameter of the tube over apatient's natural airway. In addition, increased resistance may beobserved in patients with obstructive disorders, such as COPD, asthma,etc. Higher resistance may necessitate, inter alia, a higher inspiratorytime setting (T_(I)) for delivering a prescribed pressure or volume ofgases, a higher flow setting for delivering prescribed pressure orvolume, a lower respiratory rate resulting in a higher expiratory time(T_(E)) for complete exhalation of gases, etc.

Specifically, changes in flow may be detected by evaluating various flowdata. For example, by evaluating FV loops, as described above, anincrease in resistance may be detected over a number of breaths. Thatis, upon comparing consecutive FV loops, the expiratory plot for each FVloop may reflect a progressive reduction in expiratory flow (i.e., asmaller FV loop), indicative of increasing resistance. According toother embodiments, an evaluation of end-expiratory flow (EEF) may beused to detect Auto-PEEP, as described further herein. For example, ifEEF has not reduced to zero before inspiration begins, this may indicatethat gases may still be trapped in the lungs (e.g., insufficient T_(E)to return to FRC or elevated FRC).

Pressure Data

According to embodiments, data processing module 222 may be configuredto monitor pressure. Pressure may be measured by any appropriate,internal or distributed device or sensor within the ventilatory system.For example, pressure may be monitored by proximal electromechanicaltransducers connected near the airway opening (e.g., on the inspiratorylimb, expiratory limb, at the patient interface, etc.). Alternatively,pressure may be monitored distally, at or near the lungs and/ordiaphragm of the patient.

For example, P_(Peak) and/or P_(Plat) (estimating P_(a)) may be measuredproximally (e.g., at or near the airway opening) via single-pointpressure measurements. According to embodiments, P_(Plat) (estimatingP_(a)) may be measured during an inspiratory pause maneuver (e.g.,expiratory and inspiratory valves are closed briefly at the end ofinspiration for measuring the P_(Plat) at zero flow). According to otherembodiments, circuit pressure may be measured during an expiratory pausemaneuver (e.g., expiratory and inspiratory valves are closed briefly atthe end of expiration for measuring EEP at zero flow). In this case, setPEEP may be subtracted from measured EEP for detecting Auto-PEEP.Alternatively, P_(a) may be distally measured (e.g., at or near thelungs and/or diaphragm) via multiple-point pressure measurements. Thismethod may also be useful for detecting Auto-PEEP at the end ofexpiration. According to some embodiments, triggering patients may needto be sedated before taking some of the above-described pressuremeasurements.

Data processing module 222 may be further configured to plot monitoredpressure data graphically via any suitable means. For example, accordingto embodiments, pressure data may be plotted versus time (pressurewaveform), versus volume (pressure-volume loop or PV loop), or versusany other suitable parameter as may be useful to a clinician. Accordingto embodiments, pressure may be plotted such that each breath may beindependently identified. Further, pressure may be plotted such thatinspiratory pressure and expiratory pressure may be independentlyidentified, e.g., inspiratory pressure may be represented in one colorand expiratory pressure may be represented in another color. Accordingto additional embodiments, pressure waveforms and PV loops, for example,may be represented alongside additional graphical representations, e.g.,representations of volume, flow, etc., such that a clinician maysubstantially simultaneously visualize a variety of parametersassociated with each breath.

According to embodiments, PV loops may provide useful clinical anddiagnostic information to clinicians regarding the respiratoryresistance or compliance of a patient. Specifically, upon comparing PVloops from successive breaths, an increase in resistance may be detectedwhen successive PV loops shorten and widen over time. That is, atconstant pressure, less volume is delivered to the lungs when resistanceis increasing, resulting in a shorter, wider PV loop. According toalternative embodiments, a PV loop may provide a visual representation,in the area between the inspiratory plot of pressure vs. volume and theexpiratory plot of pressure vs. volume, which is indicative ofrespiratory compliance. Further, PV loops may be compared to one anotherto determine whether compliance has changed. Additionally oralternatively, optimal compliance may be determined. That is, optimalcompliance may correspond to the dynamic compliance determined from a PVloop during a recruitment maneuver, for example.

According to additional embodiments, PV curves may be used to compareC_(S) and C_(D) over a number of breaths. For example, a first PV curvemay be plotted for C_(S) (based on P_(Plat) less EEP) and a second PVcurve may be plotted for C_(D) (based on P_(Peak) less EEP). Undernormal conditions, C_(S) and C_(D) curves may be very similar, with theC_(D) curve mimicking the C_(S) curve but shifted to the right (i.e.,plotted at higher pressure). However, in some cases the C_(D) curve mayflatten out and shift to the right relative to the C_(S) curve. Thisgraphical representation may illustrate increasing P_(t), and thusincreasing R, which may be due to mucous plugging or bronchospasm, forexample. In other cases, both the C_(D) curve and the C_(S) curves mayflatten out and shift to the right. This graphical representation mayillustrate an increase in P_(Peak) and P_(Plat), without an increase inP_(t), and thus may implicate a decrease in lung compliance, which maybe due to tension pneumothorax, atelectasis, pulmonary edema, pneumonia,bronchial intubation, etc.

As may be further appreciated, relationships between resistance, staticcompliance, dynamic compliance, and various pressure readings may giveindications of patient condition. For example, when C_(S) increases,C_(D) increases and, similarly, when R increases, C_(D) increases.Additionally, as discussed previously, P_(t) represents the differencein pressure attributable to resistive forces over elastic forces. Thus,where P_(Peak) and P_(t) are increasing with constant V_(T) delivery, Ris increasing (i.e., where P_(Peak) is increasing without a concomitantincrease in P_(Plat)). Where P_(t) is roughly constant, but whereP_(Peak) and P_(Plat) are increasing with a constant V_(T) delivery,C_(S) is increasing.

Volume Data

According to embodiments, data processing module 222 may be configuredto derive volume via any suitable means. For example, as describedabove, during volume ventilation, a prescribed V_(T) may be set fordelivery to the patient. The actual volume delivered may be derived bymonitoring the inspiratory flow over time (i.e., V=F*T). Stateddifferently, integration of flow over time will yield volume. Accordingto embodiments, V_(T) is completely delivered upon reaching T_(I).Similarly, the expiratory flow may be monitored such that expired tidalvolume (V_(TE)) may be derived. That is, under ordinary conditions, uponreaching the T_(E), the prescribed V_(T) delivered should be completelyexhaled and FRC should be reached. However, under some conditions T_(E)is inadequate for complete exhalation and FRC is not reached.

Data processing module 222 may be further configured to plot derivedvolume data graphically via any suitable means. For example, accordingto embodiments, volume data may be plotted versus time (volumewaveform), versus flow (flow-volume loop or FV loop), or versus anyother suitable parameter as may be useful to a clinician. According toembodiments, volume may be plotted such that each breath may beindependently identified. Further, volume may be plotted such thatprescribed V_(T) and V_(TE) may be independently identified, e.g.,prescribed V_(T) may be represented in one color and V_(TE) may berepresented in another color. According to additional embodiments,volume waveforms and FV loops, for example, may be represented alongsideadditional graphical representations, e.g., representations of pressure,flow, etc., such that a clinician may substantially simultaneouslyvisualize a variety of parameters associated with each breath.

Auto-PEEP Detection

Ventilator 202 may further include an Auto-PEEP detection module 224. Asdescribed above, the pressure from which a ventilator initiatesinspiration is termed the end-expiratory pressure (EEP) and, when EEP ispositive, it is termed positive end-expiratory pressure (PEEP). PEEP maybe prescribed by a clinician for various reasons. For example, for somepatients (e.g., ARDS patients), PEEP may be prescribed for supportingoxygenation and preventing alveolar collapse at the end of expiration.PEEP may also allow a reduction of F_(I)O₂ (fraction inspired oxygen) tosafe levels. However, in some cases, additional gases, i.e., in additionto the prescribed PEEP, may be trapped in the lungs at the end ofexpiration. This condition may be commonly referred to as Auto-PEEP, orintrinsic PEEP. That is, at the end of expiration, when PEEP isprescribed, EEP is equal to PEEP plus Auto-PEEP; and, where PEEP is notprescribed, EEP is equal to Auto-PEEP.

More specifically, in some cases, Auto-PEEP may result when the lungsare not sufficiently emptied during expiration before inspiration isinitiated. For example, during volume ventilation of a non-triggeringpatient, the ventilator may regulate transitions between inspiration andexpiration and between expiration and inspiration as well as therespiratory rate (RR), V_(T), flow, etc. In this case, gas-trapping mayresult when RR is too high, V_(T) is too high, flow is too low, T_(I) istoo long and/or T_(E) is too short, etc. Alternatively, during volumeventilation of a triggering patient, the patient triggers the transitionbetween expiration and inspiration, i.e., the RR. In this case,gas-trapping may result when inspiration is triggered before expirationis complete, e.g., when V_(T) is too high, flow is too low, T_(I) is toolong (resulting in T_(E) being insufficient before patient-triggeringoccurs). Specifically, when incomplete exhalation occurs, gases may betrapped in the lungs, resulting in an increased FRC. Indeed, with eachbreath, additional gases may be trapped and, not surprisingly, Auto-PEEPhas been linked to barotrauma and an increase in the work of breathing(WOB), among other conditions.

Barotrauma may result from the over-distension of alveoli, which maycause disruption of the alveolar epithelium. Further, as pressure in thealveoli increases, some alveoli may rupture, allowing gases to seep intothe perivascular sheath and into the mediastinum. This condition may bereferred to as pulmonary interstitial emphysema (PIE). Furthercomplications associated with PIE may result in a pneumothorax (i.e.,partial to complete collapse of a lung due to gases collected in thepleural cavity). Additionally or alternatively, Auto-PEEP has beenassociated with impeded venous return, which may lead to reduced cardiacoutput. Patients suffering from acute respiratory distress syndrome(ARDS) or acute lung injury (ALI) may be especially susceptible toAuto-PEEP. The work of breathing (WOB) refers to the amount of energyrequired to inhale, i.e., against forces that oppose inspiration asdescribed above. For spontaneously-breathing patients, an increased WOBmay lead to exhaustion of the respiratory muscles. Indeed, an increasedWOB may further damage and/or compromise a patient's ability to provideat least some muscular effort during respiration—potentially extendingtheir time on ventilation.

According to embodiments, Auto-PEEP may occur as a result of variouspatient conditions and/or inappropriate ventilatory settings. Thus,according to embodiments, Auto-PEEP detection module 224 may evaluatevarious ventilatory parameter data based on one or more predeterminedthresholds to detect the presence of Auto PEEP. For example, theAuto-PEEP detection module 224 may evaluate expiratory flow on a flowwaveform, or flow trace, to determine whether EEF has reached zerobefore inspiration begins. That is, if EEF breaches a predeterminedthreshold (e.g., EEF exceeds about 5 L/m), the pressure gradient betweenthe patient's lungs and the ambient surface pressure has likely notreached zero. As such, it is likely that gases have not been completelyexhaled. This condition may occur when inspiration is initiatedautomatically by the ventilator (e.g., for a non-triggering patient) orwhen inspiration is initiated via patient triggering (e.g., for aspontaneously-breathing patient). If this situation occurs over severalbreaths, it may implicate trapping of gases, or Auto-PEEP. Thus, whenEEF is positive (i.e., breaches the predetermined threshold) for severalconsecutive or substantially consecutive breaths (e.g., positive EEFdetected three or more times in ten consecutive breaths), the Auto-PEEPdetection module 224 may detect an implication of Auto-PEEP. As may beappreciated, the threshold values disclosed herein are provided asexamples only. Indeed, threshold values may be determined via anysuitable standard protocol or otherwise. Alternatively, threshold valuesmay be determined and configured for a specific patient according to aspecific prescription or otherwise.

According to further embodiments, Auto-PEEP detection module 224 mayevaluate expiratory flow on a flow trace to detect patient effort for atriggering patient. That is, by evaluating the slope of the expiratoryflow curve, the Auto-PEEP detection module 224 may determine that thepatient attempted to trigger while the patient was still activelyexhaling. That is, if T_(I) is set too high, the ventilator may take toolong to deliver the prescribed V_(T). Thereafter, a triggering patientmay attempt to initiate another inspiration prior to complete exhalationof gases, potentially trapping gases in the lungs. Thus, when patienttriggering is detected during active exhalation, the Auto-PEEP detectionmodule 224 may detect an implication of Auto-PEEP.

According to further embodiments, Auto-PEEP detection module 224 mayutilize the flow waveform to evaluate inspiratory flow based on one ormore predetermined thresholds. For example, if pressure exists in thelungs (e.g., due to Auto-PEEP), gases may not begin to flow into thelungs until the pressure in the mouth exceeds the lung pressure (i.e.,until a pressure gradient is established). That is, inspiratory flow maybe slowed at the beginning of inspiration if Auto-PEEP is present. Assuch, the Auto-PEEP detection module 224 may be configured to detectwhether inspiratory flow fails to exceed a predetermined thresholdwithin a certain amount of time after initiation of inspiration (e.g.,as automatically initiated by the ventilator based on parameter settingsfor a non-triggering patient or initiated based on ventilator detectionof patient effort and/or neural indications for a triggering patient).Thus, when inspiratory flow breaches a predetermined threshold at thebeginning of inspiration, the Auto-PEEP detection module 224 may detectan implication of Auto-PEEP.

According to further embodiments, Auto-PEEP detection module 224 mayevaluate various ventilatory parameters to determine whether respiratoryresistance is increasing. As described previously, increased resistancemay cause a decrease in flow. Consequently, T_(E) may not be adequatefor complete exhalation to FRC. Resistance may increase for a number ofreasons, as listed above, including ascites (fluid build-up in theperitoneal cavity surrounding the lungs that may increase viscous tissueresistance), chronic obstructive pulmonary disease (COPD), asthma,emphysema, mucous blockage, or otherwise. In some cases, a clinician maybe aware of a patient's obstructive condition; however, it may bedesirable for the ventilator to detect whether an obstructive disorderis worsening. Alternatively, it may be desirable for the ventilator todetect whether an obstructive disorder developing or whether resistanceis increasing for some other reason.

For example, Auto-PEEP detection module 224 may monitor ventilatory databased on one or more predetermined thresholds to determine whetherresistance is increasing. For example, where P_(t) is increasing withconstant V_(T) delivery, resistance may be increasing. Further, whereflow is decreasing with constant P_(t), resistance may be increasing(i.e., R=P_(t)/F). For example, if resistance increases by apredetermined threshold, Auto-PEEP may be implicated (e.g., resistanceincreases by about 5 cm H₂O/L/s or more). As may be appreciated, thethreshold values disclosed herein are provided as examples only. Indeed,threshold values may be determined via any suitable standard protocol orotherwise. Alternatively, threshold values may be determined andconfigured for a specific patient according to a specific prescriptionor otherwise.

Alternatively, the Auto-PEEP detection module 224 may evaluate PV curvesto compare C_(S) and C_(D) over a number of breaths to detect whetherrespiratory resistance is increasing, as described above. That is, whenthe C_(D) curve flattens out and shifts to the right relative to theC_(S) curve, this may indicate that P_(t) is increasing and, thus, thatresistance is increasing. Generally, based on the above evaluations, aninspiratory resistance may be trended over a period of time. However,according to other embodiments, expiratory resistance may also beevaluated. For example, by comparing consecutive FV loops, an expiratoryplot for each FV loop may reflect a progressive reduction in expiratoryflow indicative of increasing resistance. Consequently, if T_(E) is notlong enough for complete exhalation at the decreased flow, gases may betrapped in the lungs.

Alternatively, the Auto-PEEP detection module 224 may evaluate PV loopsfrom successive breaths to detect an increase in resistance. Forexample, increased resistance may be detected when successive PV loopsshorten and widen over time. That is, at constant pressure, less volumeis delivered to the lungs when resistance is increasing, resulting in ashorter, wider PV loop.

Alternatively, the Auto-PEEP detection module 224 may evaluate theexpiratory limb resistance of the patient circuit to detect increasedresistance. Where resistance of the expiratory limb breaches apredetermined threshold, the ventilator may recommend that the cliniciancheck the exhalation filter for mucous or other obstruction that may becausing elevated expiratory limb resistance. According to furtherembodiments, as increased expiratory limb resistance may preventcomplete exhalation, Auto-PEEP may be implicated.

As may be appreciated from the above examples, an increase in resistancemay be detected by evaluating graphical data in the form of PV curves,PV loops and/or FV loops. That is, the ventilator may determine thatresistance has increased by evaluating changes in the graphical dataand/or changes in the underlying data corresponding to the graphicaldata. Alternatively, an increase in resistance may be detected bycalculation, e.g., by measuring flow and pressure and by calculatingresistance (i.e., where compliance is constant). However, according toembodiments, when increased resistance is detected via any suitablemethod, the Auto-PEEP detection module 224 may detect an implication ofAuto-PEEP.

According to further embodiments, Auto-PEEP detection module 224 mayevaluate various ventilatory parameters to determine whether respiratorycompliance is increasing. That is, when elastance decreases (e.g.,forces opposing lung inflation), it may require less pressure to delivera particular volume (i.e., ΔV=C*ΔP). Consequently, additional volume maybe delivered at constant pressure and may over-distend the lungs and/orresult in gas-trapping. For example, Auto-PEEP detection module 224 mayevaluate PV loops based on one or more predetermined thresholds todetect whether compliance is increasing, i.e., by comparing the areabetween the inspiratory plot of pressure vs. volume and the expiratoryplot of pressure vs. volume over a number of breaths. According toalternative embodiments, Auto-PEEP detection module 224 may evaluate PVcurves to compare C_(S) and C_(D) over a number of breaths, as describedabove. That is, where both the C_(D) curve and the C_(s) curvestraighten and shift to the left (e.g., illustrating decreasing P_(Peak)and P_(Plat)) compliance may be increasing. Alternatively, theventilator may be configured with a predetermined threshold increase forcompliance (e.g., an increase of about 10 mL/cmH₂O or more), such thatAuto-PEEP may be implicated when compliance breaches the predeterminedthreshold increase. That is, if compliance increases, less pressure maybe required to deliver a prescribed V_(T) and/or lower T_(I) may berequired to deliver the prescribed V_(T). Thus, if adjustments are notmade, Auto-PEEP may result.

As may be appreciated from the above examples, an increase in compliancemay be detected by evaluating graphical data associated with PV loops orPV curves. That is, the ventilator may determine that respiratorycompliance has increased by evaluating changes in the graphical dataand/or changes in the underlying data corresponding to the graphicaldata. Alternatively, an increase in compliance may be calculated, e.g.,by determining V_(T), P_(Plat)) and EEP to calculate C_(S) or bydetermining V_(T), P_(Peak), and EEP to calculate C_(D). In either case,when increased compliance is detected, the Auto-PEEP detection module224 may detect an implication of Auto-PEEP.

According to further embodiments, the Auto-PEEP detection module 224 maycalculate the pulmonary time constant by multiplying resistance (e.g.,expiratory resistance) by compliance for a particular patient.Additionally, the Auto-PEEP detection module 224 may trend T_(E) overmultiple breaths. When T_(E) is less than three pulmonary timeconstants, T_(E) may not be adequate for complete exhalation and theAuto-PEEP detection module 224 may detect an implication of Auto-PEEP.

According to alternative embodiments, the Auto-PEEP detection module 224may trend T_(E) over multiple breaths based on one or more predeterminedthresholds to detect whether T_(E) is limited for a triggering patient.For example, if the respiratory rate (RR) is too high or flow is set toolow, the T_(E) may be limited. That is, for a triggering patient, T_(E)may not be long enough to reach FRC before inspiration is triggered,potentially resulting in Auto-PEEP. For a non-triggering patient, the RRsetting may be set too high such that T_(E) is not long enough to reachFRC before the ventilator initiates inspiration. According toembodiments, a time required to reach FRC may be calculated, e.g., basedon V_(T) and resistance and compliance data. The time required to reachFRC may then be compared to T_(E) to determine whether the time requiredto reach FRC is greater than T_(E). When the time required to reach FRCis greater than T_(E) by a predetermined threshold, for instance, it maybe determined that T_(E) is limited. Further, when limited T_(E) isdetected, the Auto-PEEP detection module 224 may detect an implicationof Auto-PEEP.

According to further embodiments, the Auto-PEEP detection module 224 mayevaluate data from an expiratory-pause maneuver. For example, anexpiratory-pause maneuver may be conducted manually by a clinician orautomatically at certain intervals during ventilation. During theexpiratory-pause maneuver, expiratory and inspiratory valves may bemomentarily shut at the end of expiration. For example, when theend-expiratory pressure (EEP) reading in the circuit exceeds set PEEP bya threshold amount (e.g., about 5 cm H₂O above set PEEP), the presenceof Auto-PEEP may be implicated. According to alternative embodiments,EEP readings may be taken by sensors at or near the patient's lungsand/or diaphragm to determine the presence of Auto-PEEP. Note that it ispreferable that the patient be sedated or non-triggering for thesemeasurements to be accurate. Thus, when EEP is greater than set PEEP atthe end of expiration for a threshold number of breaths (e.g., three ormore times in ten consecutive breaths), the Auto-PEEP detection module224 may determine that Auto-PEEP is implicated. As may be appreciated,the threshold values disclosed herein are provided as examples only.Indeed, threshold values may be determined via any suitable standardprotocol or otherwise. Alternatively, threshold values may be determinedand configured for a specific patient according to a specificprescription or otherwise.

Smart-Prompt Generation

Ventilator 202 may further include a smart prompt module 226. Asdescribed above, the presence of Auto-PEEP may be very difficult for aclinician to detect. As may be appreciated, multiple ventilatoryparameters may be monitored and evaluated in order to detect animplication of Auto-PEEP. In addition, when Auto-PEEP is implicated,many clinicians may not be aware of adjustments to ventilatoryparameters that may reduce or eliminate Auto-PEEP. As such, upondetection of Auto-PEEP, the smart prompt module 226 may be configured tonotify the clinician that Auto-PEEP is implicated and/or to providerecommendations to the clinician for mitigating Auto-PEEP. For example,smart prompt module 226 may be configured to notify the clinician bydisplaying a smart prompt on display monitor 204 and/or within a windowof the GUI. According to additional embodiments, the smart prompt may becommunicated to and/or displayed on a remote monitoring systemcommunicatively coupled to ventilatory system 200. Alternatively, in anautomated embodiment, the smart prompt module 226 may communicate with aventilator control system so that the recommendation may beautomatically implemented to mitigate Auto-PEEP.

In order to accomplish the various aspects of the notification and/orrecommendation message display, the smart prompt module 226 maycommunicate with various other components and/or modules. For instance,smart prompt module 226 may be in communication with data processingmodule 222, Auto-PEEP detection module 224, or any other suitable moduleor component of the ventilatory system 200. That is, smart prompt module226 may receive an indication that Auto-PEEP has been implicated by anysuitable means. In addition, smart prompt module 226 may receiveinformation regarding one or more parameters that implicated thepresence of Auto-PEEP and information regarding the patient'sventilatory settings and treatment. Further, according to someembodiments, the smart prompt module 226 may have access to a patient'sdiagnostic information (e.g., regarding whether the patient has ARDS,COPD, asthma, emphysema, or any other disease, disorder, or condition).

Smart prompt module 226 may further comprise additional modules formaking notifications and/or recommendations to a clinician regarding thepresence of Auto-PEEP. For example, according to embodiments, smartprompt module 226 may include a notification module 228 and arecommendation module 230. For instance, smart prompts may be providedaccording to a hierarchical structure such that a notification messagesand/or a recommendation message may be initially presented in summarizedform and, upon clinician selection, an additional detailed notificationand/or recommendation message may be displayed. According to alternativeembodiments, a notification message may be initially presented and, uponclinician selection, a recommendation message may be displayed.Alternatively or additionally, the notification message may besimultaneously displayed with the recommendation message in any suitableformat or configuration.

Specifically, according to embodiments, the notification message mayalert the clinician as to the detection of a patient condition, a changein patient condition, or an effectiveness of ventilatory treatment. Forexample, the notification message may alert the clinician that Auto-PEEPhas been detected. The notification message may further alert theclinician regarding the particular ventilatory parameter(s) thatimplicated Auto-PEEP (e.g., positive EEF over the last n breaths,decreased flow over the past n breaths at constant V_(T), increasedresistance, etc.)

Additionally, according to embodiments, the recommendation message mayprovide various suggestions to the clinician for addressing a detectedcondition. That is, if Auto-PEEP has been detected, the recommendationmessage may suggest that the clinician reduce V_(T), increase flow,increase T_(E) by decreasing RR and/or T_(I), etc. According toadditional embodiments, the recommendation message may be based on theparticular ventilatory parameter(s) that implicated Auto-PEEP.Additionally or alternatively, the recommendation message may be basedon current ventilatory settings such that suggestions are directed to aparticular patient's treatment. Additionally or alternatively, therecommendation message may be based on a diagnosis and/or other patientattributes. Further still, the recommendation message may include aprimary recommendation message and a secondary recommendation message.

As described above, smart prompt module 226 may also be configured withnotification module 228 and recommendation module 230. The notificationmodule 228 may be in communication with data processing module 222,Auto-PEEP detection module 224, or any other suitable module to receivean indication that Auto-PEEP has been detected. Notification module 228may be responsible for generating a notification message via anysuitable means. For example, the notification message may be provided asa tab, banner, dialog box, or other similar type of display. Further,the notification messages may be provided along a border of thegraphical user interface, near an alarm display or bar, or in any othersuitable location. A shape and size of the notification message mayfurther be optimized for easy viewing with minimal interference to otherventilatory displays. The notification message may be further configuredwith a combination of icons and text such that the clinician may readilyidentify the message as a notification message.

The recommendation module 230 may be responsible for generating one ormore recommendation messages via any suitable means. The one or morerecommendation messages may provide suggestions and informationregarding addressing a detected condition and may be accessible from thenotification message. For example, the one or more recommendationmessages may identify the parameters that implicated the detectedcondition, may provide suggestions for adjusting one or more ventilatoryparameters to address the detected condition, may provide suggestionsfor checking ventilatory equipment or patient position, or may provideother helpful information, Specifically, the one or more recommendationmessages may provide suggestions and information regarding Auto-PEEP.

According to embodiments, based on the particular parameters thatimplicated Auto-PEEP, the recommendation module may provide suggestionsfor addressing Auto-PEEP. That is, if Auto-PEEP was implicated bypositive EEF over several breaths, the one or more recommendationmessages may include suggesting increasing set flow, adjusting settingssuch that EEF approximates zero, lowering RR such that T_(E) may beincreased, lowering V_(T) such that T_(E) may be adequate, etc.Alternatively, if Auto-PEEP was implicated by increased resistance, theone or more recommendation messages may include suggesting suctioningthe patient interface, adjusting patient position, delivering abronchodialator or other suitable medication, etc.

Additionally or alternatively, the one or more recommendation messagesmay also be based on current ventilatory settings for the patient. Forexample, if Auto-PEEP was implicated by positive EEF over severalbreaths, but where the patient's current ventilatory settings include ahigh flow setting, the one or more recommendation messages may notsuggest increasing set flow.

Additionally or alternatively, the one or more recommendation messagesmay be based on a patient's diagnosis or other clinical data. Accordingto some embodiments, if a patient has been diagnosed with COPD, theventilator may be configured with adjusted thresholds such thatsensitivity to resistance is increased (i.e., a lower predeterminedthreshold) or decreased (i.e., a higher predetermined threshold) basedon clinician input or otherwise. According to some embodiments, if apatient has been diagnosed with emphysema, the ventilator may beconfigured with adjusted thresholds such that sensitivity to complianceis increased (i.e., a lower predetermined threshold) or decreased (i.e.,a higher predetermined threshold) based on clinician input or otherwise.According to other embodiments, if a patient has been diagnosed withARDS, the ventilator may be aware that the patient is at higher risk forAuto-PEEP and may configured with increased sensitivity for detectingimplications of Auto-PEEP. Alternatively, Auto-PEEP may be desirable foran ARDS patient (e.g., preventing alveolar collapse and increasingoxygenation) and the ventilator may be configured with decreasedsensitivity for detecting implications of Auto-PEEP. When Auto-PEEP isdetected, the one or more recommendation messages may include suggestingdecreasing RR, increasing flow, increasing T_(E), decreasing V_(T), etc.

According to still other embodiments, the recommendation message mayinclude a primary message and a secondary message. That is, a primarymessage may provide suggestions that are specifically targeted to thedetected condition based on the particular parameters that implicatedthe condition. Alternatively, the primary message may providesuggestions that may provide a higher likelihood of mitigating thedetected condition. The secondary message may provide more generalsuggestions and/or information that may aid the clinician in furtheraddressing and/or mitigating the detected condition. For example, theprimary message may provide a specific suggestion for adjusting aparticular parameter to mitigate the detected condition (e.g., considerincreasing flow and/or adjust settings such that EEF approximates zero).Alternatively, the secondary message may provide general suggestions foraddressing the detected condition (e.g., consider other steps forincreasing T_(E) such as decreasing V_(T) or switching to a square flowwaveform).

Smart prompt module 226 may also be configured such that notificationand/or recommendation messages may be displayed in a partiallytransparent window or format. The transparency may allow fornotification and/or recommendation messages to be displayed such thatnormal ventilator GUI and respiratory data may be visualized behind themessages. This feature may be particularly useful for displayingdetailed messages. As described previously, notification and/orrecommendation messages may be displayed in areas of the display screenthat are either blank or that cause minimal distraction from therespiratory data and other graphical representations provided by theGUI. However, upon selective expansion of a message, respiratory dataand graphs may be at least partially obscured. As a result, translucentdisplay may provide the detailed message such that it is partiallytransparent. Thus, graphical and other data may be visible behind thedetailed alarm message.

Additionally, notification and/or recommendation messages may provideimmediate access to the display and/or settings screens associated withthe detected condition. For example, an associated parameter settingsscreen may be accessed from a notification and/or a recommendationmessage via a hyperlink such that the clinician may address the detectedcondition as necessary. An associated parameter display screen may alsobe accessed such that the clinician may view clinical data associatedwith the detected condition in the form of charts, graphs, or otherwise.That is, according to embodiments, the clinician may access theventilatory data that implicated the detected condition for verificationpurposes. For example, when Auto-PEEP has been implicated, depending onthe particular ventilatory parameters that implicated Auto-PEEP, theclinician may be able to access ventilatory settings for addressingAuto-PEEP (e.g., a settings screen for adjusting V_(T), T_(I), flow,etc.) and/or to view associated ventilatory parameters that implicatedAuto-PEEP (e.g., a graphics screen displaying historical flow waveforms,volume waveforms, and/or pressure waveforms that gave rise toimplications of Auto-PEEP).

According to embodiments, upon viewing the notification and/orrecommendation messages, upon addressing the detected condition byadjusting one or more ventilatory settings or otherwise, or upon manualselection, the notification and/or recommendation messages may becleared from the graphical user interface.

Auto-PEEP Detection during Volume Ventilation of Non-Triggering Patient

FIG. 3 is a flow chart illustrating an embodiment of a method fordetecting an implication of Auto-PEEP.

As should be appreciated, the particular steps and methods describedherein are not exclusive and, as will be understood by those skilled inthe art, the particular ordering of steps as described herein is notintended to limit the method, e.g., steps may be performed in differingorder, additional steps may be performed, and disclosed steps may beexcluded without departing from the spirit of the present methods.

The illustrated embodiment of the method 300 depicts a method fordetecting Auto-PEEP during volume ventilation of a non-triggeringpatient. Method 300 begins with an initiate ventilation operation 302.Initiate ventilation operation 302 may further include variousadditional operations. For example, initiate ventilation operation 302may include receiving one or more ventilatory settings associated withventilation of a patient (e.g., at receive settings operation 304). Forexample, the ventilator may be configured to provide volume ventilationto a non-triggering patient. As such, the ventilatory settings and inputreceived may include a prescribed V_(T), set flow (or peak flow),predicted or ideal body weight (PBW or IBW), RR, etc. According to someembodiments, a predicted T_(E) may be determined based on normalrespiratory and compliance values or value ranges based on the patient'sPBW or IBW. According to some embodiments, respiratory resistance anddynamic compliance data may be trended for the patient duringventilation to determine whether the data actually falls within normalranges.

According to some embodiments, initiate ventilation operation 302 mayfurther include receiving diagnostic information regarding the patient(e.g., at receive diagnosis operation 306, represented with dashed linesto identify the operation as optional). For example, according toembodiments, the clinician may indicate that the patient has beendiagnosed with ARDS, COPD, emphysema, asthma, etc. The ventilator may befurther configured to associate a patient diagnosis with variousconditions (e.g., increased resistance associated with COPD, increasedlikelihood of alveolar collapse associated with ARDS, etc.).

At deliver ventilation operation 308, the ventilator provides volumeventilation to a non-triggering patient, as described above. That is,according to embodiments, the ventilator provides ventilation based on aprescribed V_(T). For example, the ventilator may deliver gases to thepatient at a set flow for a set T_(I) at a set RR. When prescribed V_(T)has been delivered, the ventilator may initiate the expiratory phase.

While volume ventilation is being delivered, the ventilator may conductvarious data processing operations. For example, at data processingoperation 310, the ventilator may collect and/or derive variousventilatory parameter data associated with volume ventilation of thenon-triggering patient. For example, as described above, the ventilatormay collect data regarding flow and pressure parameters. Additionally,the ventilator may derive various ventilatory parameter data based onthe collected data, e.g., volume, respiratory resistance, respiratorycompliance, etc. As described previously, measurements for respiratoryresistance and/or compliance may be trended continuously for anon-triggering patient because ventilatory data may be obtained withoutsedating the patient or otherwise. Additionally, the ventilator maygenerate various graphical representations of the collected and/orderived ventilatory parameter data, e.g., flow waveforms, pressurewaveforms, pressure-volume loops, flow-volume loops, etc.

At analyze operation 312, the ventilator may evaluate collected and/orderived data to determine whether a certain patient condition exists.For example, according to embodiments, the ventilator may evaluate thevarious collected and derived parameter data, including EEF, T_(E), EEP,respiratory resistance and/or compliance, P_(a), patient effort, etc.,based on one or more predetermined thresholds. According to embodiments,the ventilator may further evaluate the ventilatory parameter data inlight of the patient's specific parameter settings, including V_(T), setflow, set T_(I), etc., and/or the patient's diagnostic information.

According to some embodiments, at detect operation 314 the ventilatormay determine whether Auto-PEEP is implicated based on evaluating EEF atanalyze operation 312. For example, according to embodiments, theventilator may be configured with a threshold value for EEF. Forexample, if EEF is greater than or equal to about 5 L/m when inspirationis initiated, the threshold may be breached and positive EEF may bedetected (e.g., when EEF is greater than or equal to 5 L/m). Further,according to embodiments, the ventilator may be configured with athreshold number of breaths, e.g., if positive EEF is detected three ormore times in ten consecutive breaths the threshold may be breached.That is, when three or more of ten consecutive breaths exhibit positiveEEF, it may be determined that Auto-PEEP is implicated.

According to alternative embodiments, the ventilator may further takeinto account a patient's diagnosis to determine whether Auto-PEEP islikely, as described above. For example, if a patient has been diagnosedwith ARDS, the ventilator may determine that Auto-PEEP is more likelyand may be configured with additional sensitivity to changes in theabove parameters (e.g., detection of positive EEF two or more times inten consecutive breaths may breach a threshold for an ARDS patient). IfAuto-PEEP is implicated, the operation may proceed to issue smart promptoperation 316. If Auto-PEEP is not implicated, the operation may returnto analyze operation 312.

According to still other embodiments, at detect operation 314 theventilator may determine whether Auto-PEEP is implicated based onevaluating EEP at analyze operation 312. According to embodiments, EEPmay be measured distally via any suitable method (e.g., by one or morepressure transducers at or near the lungs and/or diaphragm).Alternatively, EEP may be measured proximally via any suitable method(e.g., during an expiratory hold maneuver). If EEP in excess of set PEEP(if any) is detected at the end of expiration, Auto-PEEP may beimplicated. According to embodiments, the ventilator may be configuredwith a threshold value for EEP (e.g., about 5 cm H₂O above set PEEP).Further, according to embodiments, the ventilator may be configured witha threshold number of breaths, e.g., excess pressure detected three ormore times in ten consecutive breaths may breach the threshold. That is,when three or more of ten consecutive breaths exhibit excess pressure atthe end of expiration, it may be determined that Auto-PEEP isimplicated. If Auto-PEEP is implicated, the operation may proceed toissue smart prompt operation 316. If Auto-PEEP is not implicated, theoperation may return to analyze operation 312.

According to other embodiments, at detect operation 314 the ventilatormay determine whether Auto-PEEP is implicated based on evaluatingresistance and/or compliance at analyze operation 312. According toembodiments, the ventilator may be configured with a predeterminedthreshold increase for resistance. For example, if resistance increasesby about 5 cm H₂O/L/s or more, it may be determined that Auto-PEEP isimplicated. Alternatively, the ventilator may be configured with apredetermined threshold increase for compliance. For example, ifcompliance increases by about 10 mL/cm H₂O or more, it may be determinedthat Auto-PEEP is implicated. If Auto-PEEP is implicated, the operationmay proceed to issue smart prompt operation 316. If Auto-PEEP is notimplicated, the operation may return to analyze operation 312.

According to other embodiments, at detect operation 314 the ventilatormay evaluate respiratory resistance data and respiratory compliance datato calculate a time required to reach functional residual capacity(FRC). Thereafter, the time required to reach FRC may be compared to theT_(E). According to embodiments, when the time required to reach FRC isgreater than the T_(E) by a predetermined threshold, it may bedetermined that Auto-PEEP is implicated. If Auto-PEEP is implicated, theoperation may proceed to issue smart prompt operation 316. If Auto-PEEPis not implicated, the operation may return to analyze operation 312.

According to further embodiments, at detect operation 314 the ventilatormay evaluate the pulmonary time constant and T_(E). That is, bymultiplying resistance (e.g., expiratory resistance) by compliance theventilator may calculate the pulmonary time constant. The ventilator mayalso trend T_(E) over multiple breaths for the non-triggering patient.When T_(E) is less than three pulmonary time constants, T_(E) may not beadequate for complete exhalation and the ventilator may detect animplication of Auto-PEEP. If Auto-PEEP is implicated, the operation mayproceed to issue smart prompt operation 316. If Auto-PEEP is notimplicated, the operation may return to analyze operation 312.

As may be appreciated, the ventilator may determine whether Auto-PEEP isimplicated at detect operation 314 via any suitable means. Indeed, anyof the above described ventilatory parameters may be evaluated accordingto various thresholds for detecting Auto-PEEP. Further, the disclosureregarding specific ventilatory parameters as they may implicateAuto-PEEP is not intended to be limiting. In fact, any suitableventilatory parameter may be monitored and evaluated for detectingAuto-PEEP within the spirit of the present disclosure. As such, ifAuto-PEEP is implicated via any suitable means, the operation mayproceed to issue smart prompt operation 316. If Auto-PEEP is notimplicated, the operation may return to analyze operation 312.

At issue smart prompt operation 316, the ventilator may alert theclinician via any suitable means that Auto-PEEP has been implicated. Forexample, according to embodiments, the ventilator may display a smartprompt including a notification message and/or a recommendation messageregarding the detection of Auto-PEEP on the GUI. According toalternative embodiments, the ventilator may communicate the smartprompt, including the notification message and/or the recommendationmessage, to a remote monitoring system communicatively coupled to theventilator.

According to embodiments, the notification message may alert theclinician that Auto-PEEP has been detected and, optionally, may provideinformation regarding the ventilatory parameter(s) that implicatedAuto-PEEP. According to additional embodiments, the recommendationmessage may provide one or more suggestions for mitigating Auto-PEEP.According to further embodiments, the one or more suggestions may bebased on the patient's particular ventilatory settings and/or diagnosis.According to some embodiments, the clinician may access one or moreparameter setting and/or display screens from the smart prompt via ahyperlink or otherwise for addressing Auto-PEEP. According to additionalor alternative embodiments, a clinician may remotely access one or moreparameter and/or display screens from the smart prompt via a hyperlinkor otherwise for remotely addressing Auto-PEEP.

Smart Prompt Generation regarding Auto-PEEP Detection

FIG. 4 is a flow chart illustrating an embodiment of a method forissuing a smart prompt upon detecting an implication of Auto-PEEP.

As should be appreciated, the particular steps and methods describedherein are not exclusive and, as will be understood by those skilled inthe art, the particular ordering of steps as described herein is notintended to limit the method, e.g., steps may be performed in differingorder, additional steps may be performed, and disclosed steps may beexcluded without departing from the spirit of the present methods.

The illustrated embodiment of the method 400 depicts a method forissuing a smart prompt upon detecting Auto-PEEP during volumeventilation of a non-triggering patient. Method 400 begins with detectoperation 402, wherein the ventilator detects that Auto-PEEP isimplicated, as described above in method 300,

At identify ventilatory parameters operation 404, the ventilator mayidentify one or more ventilatory parameters that implicated Auto-PEEP.For example, the ventilator may recognize that Auto-PEEP was implicatedby positive EEF over several breaths. Alternatively, the ventilator mayrecognize that Auto-PEEP was implicated by excess EEP over PEEP.Alternatively, the ventilator may recognize that Auto-PEEP wasimplicated by increased resistance and/or compliance. Alternatively, theventilator may recognize that Auto-PEEP was implicated by determiningthe time required to reach FRC is greater than T_(E). As may beappreciated, the ventilator may use information regarding ventilatoryparameters that implicated Auto-PEEP in determining an appropriatenotification and/or recommendation message of the smart prompt.

At identify settings operation 406, the ventilator may identify one ormore current ventilatory settings associated with the ventilatorytreatment of the patient. For example, current ventilatory settings mayhave been received upon initiating ventilation for the patient and mayhave been determined by the clinician or otherwise (e.g., by evaluatinga patient diagnosis, oxygenation, PBW or IBW, disease conditions, etc.).For instance, current ventilatory settings associated with volumeventilation for a non-triggering patient may include, inter alia,prescribed V_(T), flow, RR, T_(I), etc. In addition, a predicted TE mayhave been determined based on normal respiratory resistance andcompliance values and the patient's PBW or IBW. As may be appreciated,the ventilator may use information regarding current ventilatorysettings in determining an appropriate notification and/orrecommendation message of the smart prompt.

At identify patient diagnosis operation 408, the ventilator mayoptionally identify patient diagnosis information received from aclinician (represented with dashed lines to identify the operation asoptional). For example, according to embodiments, the clinician mayindicate during ventilation initiation or otherwise that the patient wasdiagnosed with COPD, ARDS, emphysema, asthma, etc. As may beappreciated, the ventilator may use information regarding a patient'sdiagnosis in determining an appropriate notification and/orrecommendation message of the smart prompt.

At determine operation 410, the ventilator may determine an appropriatenotification message. For example, the appropriate notification messagemay alert the clinician that Auto-PEEP has been implicated and,optionally, may provide information regarding the ventilatoryparameter(s) that implicated Auto-PEEP. For example, the appropriatenotification may alert the clinician that Auto-PEEP was implicated bypositive EEF over several breaths, Auto-PEEP was implicated by excessEEP over several breaths, or Auto-PEEP was implicated by increasedresistance.

At determine operation 412, the ventilator may determine an appropriateprimary recommendation message. The appropriate primary recommendationmessage may provide one or more specific suggestions for mitigatingAuto-PEEP. For example, according to some embodiments, in determiningthe appropriate primary recommendation message, the ventilator may takeinto consideration the one or more monitored ventilatory parameters thatimplicated Auto-PEEP. That is, if Auto-PEEP was implicated by positiveEEF over several breaths, the ventilator may offer one or morerecommendation messages that may include: “Consider increasingrespiratory rate and/or set flow to shorten T_(I); Adjust settings untilEEF approximates zero; Investigate reasons for increased resistanceand/or compliance,” for example. Alternatively, if Auto-PEEP wasimplicated by increased resistance, the one or more recommendationmessages may include suggesting suctioning the patient interface,adjusting patient position, delivering a bronchodialator or othersuitable medication, etc.

According to other embodiments, in determining an appropriate primaryrecommendation message the ventilator may take into consideration thepatient's current ventilatory settings. That is, if set flow is alreadyhigh, the ventilator may not suggest increasing the set flow. In thiscase, the primary recommendation message may rather suggest decreasingV_(T), or may provide another suitable specific suggestion. According tofurther embodiments, in determining the appropriate primaryrecommendation message the ventilator may take into consideration thepatient's diagnosis. For example, if a patient has been diagnosed withARDS, in determining an appropriate primary recommendation message, theventilator may make a specific suggestion for changing patient positionrather than decreasing V_(T) (e.g., as high V_(T) may be necessary foradequate oxygenation of an ARDS patient).

At determine operation 414, the ventilator may determine an appropriatesecondary recommendation message. The secondary recommendation messagemay provide one or more general suggestions for mitigating Auto-PEEP.For example, the secondary recommendation message may include: “Considerother steps for increasing T_(E), such as decreasing V_(T) or switchingto a square flow waveform.” The secondary recommendation message mayprovide additional recommendations for mitigating Auto-PEEP.

At issue smart prompt operation 416, the ventilator may alert theclinician via any suitable means that Auto-PEEP has been implicated. Forexample, according to embodiments, a smart prompt may include anappropriate notification message and an appropriate recommendationmessage regarding the presence of Auto-PEEP. Additionally oralternatively, the smart prompt may include an appropriate notificationmessage, an appropriate primary recommendation message, and anappropriate secondary recommendation message. The smart prompt may bedisplayed via any suitable means, e.g., on the ventilator GUI and/or ata remote monitoring station, such that the clinician is alerted as tothe potential presence of Auto-PEEP and offered additional informationand/or recommendations for mitigating the Auto-PEEP, as describedherein.

Ventilator GUI Display of Initial Smart Prompt

FIG. 5 is an illustration of an embodiment of a graphical user interfacedisplaying a smart prompt having a notification message.

Graphical user interface 500 may display various monitored and/orderived data to the clinician during ventilation of a patient. Inaddition, graphical user interface 500 may display various messages tothe clinician (e.g., alarm messages, etc.). Specifically, graphical userinterface 500 may display a smart prompt as described herein.

According to embodiments, the ventilator may monitor and evaluatevarious ventilatory parameters based on one or more predeterminedthresholds to detect Auto-PEEP. As illustrated, a flow waveform may begenerated and displayed by the ventilator on graphical user interface500. As further illustrated, the flow waveform may be displayed suchthat inspiratory flow 502 is represented in a different color (e.g.,green) than expiratory flow 504 (e.g., yellow). Although expiratory flowmay preferably approximate zero at the end of expiration, in someinstances EEF may not reach zero before inspiration begins, asillustrated by positive EEF 506. According to further embodiments,positive EEF may be identified by a positive EEF icon 508, or otheridentifier, such that a clinician may readily identify positive EEF onthe flow waveform. Additionally or alternatively, the flow waveform maybe frozen for a period of time such that the clinician may be alerted asto the position in time of the incidence of positive EEF along the flowwaveform. Additionally or alternatively, positive EEF icon 508 may alsoinclude an informative text message indicating that positive EEF wasdetected.

That is, positive EEF may be detected if EEF breaches a predeterminedthreshold associated with EEF (e.g., if EEF exceeds about 5 L/m).According to embodiments, when positive EEF is detected in a thresholdnumber of breaths, e.g., three or more times in ten consecutive breaths,the ventilator may determine that Auto-PEEP is implicated. According toother embodiments, when resistance increases by a predeterminedthreshold (e.g., about 5 cm H₂O/L/s or more), the ventilator maydetermine that Auto-PEEP is implicated. According to furtherembodiments, when compliance increases by a predetermined threshold(e.g., about 10 mL/cm H₂O or more), the ventilator may determine thatAuto-PEEP is implicated. According to further embodiments, e.g., whenEEP exceeds PEEP by a threshold amount for a threshold number of breaths(e.g., about 5 cm H₂O above set PEEP detected in three or more of tenconsecutive breaths), the ventilator may determine that Auto-PEEP isimplicated. Upon a determination that Auto-PEEP is implicated, thegraphical user interface 500 may display a smart prompt, e.g., smartprompt 510.

According to embodiments, smart prompt 510 may be displayed in anysuitable location such that a clinician may be alerted regarding adetected patient condition, but while allowing other ventilatorydisplays and data to be visualized substantially simultaneously. Asillustrated, smart prompt 510 is presented as a bar or banner across anupper region of the graphical user interface 500. However, as previouslynoted, smart prompt 510 may be displayed as a tab, icon, button, banner,bar, or any other suitable shape or form. Further, smart prompt 510 maybe displayed in any suitable location within the graphical userinterface 500. For example, smart prompt 510 may be located along anyborder region of the graphical user interface 500 (e.g., top, bottom, orside borders) (not shown), across an upper region (shown), or in anyother suitable location. Further, as described herein, smart prompt 510may be partially transparent (not shown) such that ventilatory displaysand data may be at least partially visible behind smart prompt 510.

Specifically, smart prompt 510 may alert the clinician that Auto-PEEPhas been detected, for example by notification message 512. As describedherein, notification message 512 may alert the clinician that Auto-PEEPis implicated via any suitable means, e.g., “Auto-PEEP Alert” (shown),“Auto-PEEP Detected” (not shown), or “Auto-PEEP Implicated” (not shown).Smart prompt 510 may further include information regarding ventilatoryparameters that implicated Auto-PEEP. For example, if Auto-PEEP wasdetected based on a positive EEF over multiple breaths, this informationmay be provided to the clinician (e.g., “Positive EEF detected 3 or moretimes in last 10 breaths,” shown). According to the illustratedembodiment, parameter information 514 is provided along with thenotification message 512 in a banner. According to alternativeembodiments, in addition to the notification message 512 and theparameter information 514, one or more recommendation messages may beprovided in an initial smart prompt banner (not shown). According toother embodiments, rather than providing information regardingventilatory parameters that implicated Auto-PEEP in the initial smartprompt, this information may be provided within an expanded portion (notshown) of smart prompt 510.

According to embodiments, smart prompt 510 may be expanded to provideadditional information and/or recommendations to the clinician regardinga detected patient condition. For example, an expand icon 516 may beprovided within a suitable area of the smart prompt 510. According toembodiments, upon selection of the expand icon 516 via any suitablemeans, the clinician may optionally expand the smart prompt 510 toacquire additional information and/or recommendations for mitigating thedetected patient condition. According to further embodiments, smartprompt 510 may include links (not shown) to additional settings and/ordisplay screens of the graphical user interface 500 such that theclinician may easily and quickly mitigate and/or verify the detectedcondition.

As may be appreciated, the disclosed data, graphics, and smart promptillustrated in graphical user interface 500 may be arranged in anysuitable order or configuration such that information and alerts may becommunicated to the clinician in an efficient and orderly manner. Thedisclosed data, graphics, and smart prompt are not to be understood asan exclusive array, as any number of similar suitable elements may bedisplayed for the clinician within the spirit of the present disclosure.Further, the disclosed data, graphics, and smart prompt are not to beunderstood as a necessary array, as any number of the disclosed elementsmay be appropriately replaced by other suitable elements withoutdeparting from the spirit of the present disclosure. The illustratedembodiment of the graphical user interface 500 is provided as an exampleonly, including potentially useful information and alerts that may beprovided to the clinician to facilitate communication of detectedAuto-PEEP in an orderly and informative way, as described herein.

Ventilator GUI Display of Expanded Smart Prompt

FIG. 6 is an illustration of an embodiment of a graphical user interfacedisplaying an expanded smart prompt having a notification message andone or more recommendation messages.

Graphical user interface 600 may display various monitored and/orderived data to the clinician during ventilation of a patient. Inaddition, graphical user interface 600 may display an expanded smartprompt including one or more recommendation messages as describedherein.

According to embodiments, as described above, an expand icon 604 may beprovided within a suitable area of smart prompt 602. Upon selection ofthe expand icon 604, the clinician may optionally expand smart prompt602 to acquire additional information and/or recommendations formitigating the detected patient condition. For example, expanded smartprompt 606 may be provided upon selection of expand icon 604. Asdescribed above for smart prompt 510, expanded smart prompt 606 may bedisplayed as a tab, icon, button, banner, bar, or any other suitableshape or form. Further, expanded smart prompt 606 may be displayed inany suitable location within the graphical user interface 600. Forexample, expanded smart prompt 606 may be displayed below (shown) smartprompt 602, to a side (not shown) of smart prompt 602, or otherwiselogically associated with smart prompt 602. According to otherembodiments, an initial smart prompt may be hidden (not shown) upondisplaying expanded smart prompt 606. Expanded smart prompt 606 may alsobe partially transparent (not shown) such that ventilatory displays anddata may be at least partially visible behind expanded smart prompt 606.

According to embodiments, expanded smart prompt 606 may compriseadditional information (not shown) and/or one or more recommendationmessages 608 regarding detected Auto-PEEP. For example, the one or morerecommendation messages 608 may include a primary recommendation messageand a secondary recommendation message. The primary recommendationmessage may provide one or more specific suggestions for mitigatingAuto-PEEP during volume ventilation of a non-triggering patient. Forexample, if Auto-PEEP was implicated by positive EEF over severalbreaths, the one or more recommendation messages may include: “Considerincreasing respiratory rate and/or set flow to shorten T_(I); Adjustsettings until EEF approximates zero; Investigate reasons for increasedresistance and/or compliance.” Alternately, if Auto-PEEP was implicatedby increased resistance, the one or more recommendation messages mayalso include suctioning the patient interface, repositioning thepatient, etc. The secondary recommendation message may provide one ormore general suggestions for mitigating Auto-PEEP. For example, thesecondary recommendation message may include: “Consider other steps forincreasing T_(E), such as decreasing V_(T) or switching to a square flowwaveform.”

According to embodiments, expanded smart prompt 606 may also include oneor more hyperlinks 610, which may provide immediate access to thedisplay and/or settings screens associated with detected Auto-PEEP. Forexample, associated parameter settings screens may be accessed fromexpanded smart prompt 606 via hyperlink 610 such that the clinician mayaddress detected Auto-PEEP by adjusting one or more parameter settingsas necessary. Alternatively, associated parameter display screens may beaccessed such that the clinician may view clinical data associated withAuto-PEEP in the form of charts, graphs, or otherwise. That is,according to embodiments, the clinician may access the ventilatory datathat implicated Auto-PEEP for verification purposes. For example, whenAuto-PEEP has been implicated, depending on the particular ventilatoryparameters that implicated Auto-PEEP, the clinician may be able toaccess associated parameter settings screens for addressing Auto-PEEP(e.g., settings screens for adjusting V_(T), T_(I), RR, flow, etc.).Additionally or alternatively, the clinician may be able to accessand/or view display screens associated with the ventilatory parametersthat implicated Auto-PEEP (e.g., a graphics screen displaying historicalflow waveforms, volume waveforms, and/or pressure waveforms that gaverise to implications of Auto-PEEP).

As may be appreciated, the disclosed smart prompt and recommendationmessages illustrated in graphical user interface 600 may be arranged inany suitable order or configuration such that information and alerts maybe communicated to the clinician in an efficient and orderly manner.Indeed, the illustrated embodiment of the graphical user interface 600is provided as an example only, including potentially useful informationand recommendations that may be provided to the clinician to facilitatecommunication of suggestions for mitigating detected Auto-PEEP in anorderly and informative way, as described herein.

Unless otherwise indicated, all numbers expressing measurements,dimensions, and so forth used in the specification and claims are to beunderstood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired propertiessought to be obtained by the present disclosure. Further, unlessotherwise stated, the term “about” shall expressly include “exactly,”consistent with the discussions regarding ranges and numerical data.Concentrations, amounts, and other numerical data may be expressed orpresented herein in a range format. It is to be understood that such arange format is used merely for convenience and brevity and thus shouldbe interpreted flexibly to include not only the numerical valuesexplicitly recited as the limits of the range, but also to include allthe individual numerical values or sub-ranges encompassed within thatrange as if each numerical value and sub-range is explicitly recited. Asan illustration, a numerical range of “about 4 percent to about 7percent” should be interpreted to include not only the explicitlyrecited values of about 4 percent to about 7 percent, but also includeindividual values and sub-ranges within the indicated range. Thus,included in this numerical range are individual values such as 4.5, 5.25and 6 and sub-ranges such as from 4-5, from 5-7, and from 5.5-6.5, etc.This same principle applies to ranges reciting only one numerical value.Furthermore, such an interpretation should apply regardless of thebreadth of the range or the characteristics being described.

It will be clear that the systems and methods described herein are welladapted to attain the ends and advantages mentioned as well as thoseinherent therein. Those skilled in the art will recognize that themethods and systems within this specification may be implemented in manymanners and as such is not to be limited by the foregoing exemplifiedembodiments and examples. In other words, functional elements beingperformed by a single or multiple components, in various combinations ofhardware and software, and individual functions can be distributed amongsoftware applications at either the client or server level. In thisregard, any number of the features of the different embodimentsdescribed herein may be combined into one single embodiment andalternative embodiments having fewer than or more than all of thefeatures herein described are possible.

While various embodiments have been described for purposes of thisdisclosure, various changes and modifications may be made which are wellwithin the scope of the present disclosure. Numerous other changes maybe made which will readily suggest themselves to those skilled in theart and which are encompassed in the spirit of the disclosure and asdefined in the appended claims.

What is claimed is:
 1. A ventilator-implemented method for detectingAuto-PEEP during ventilation of a non-triggering patient, the methodimplemented by a ventilator having at least one processor, the methodcomprising: receiving one or more ventilatory settings associated withventilation of the non-triggering patient; determining one or morepredetermined thresholds for detecting Auto-PEEP based at least in parton the one or more ventilatory settings; monitoring ventilation of thenon-triggering patient to obtain ventilatory data; determining, by theat least one processor, that Auto-PEEP is implicated for thenon-triggering patient upon detecting that the ventilatory data breachesthe one or more predetermined thresholds; determining a list of entriesfor mitigating Auto-PEEP based at least in part on identifying thepatient as non-triggering, wherein at least one entry of the list ofentries is different for the non-triggering patient than for atriggering patient; and issuing a prompt when Auto-PEEP is implicated,the prompt displaying: a notification that Auto-PEEP is implicated; andthe list of entries for mitigating Auto-PEEP.
 2. Theventilator-implemented method of claim 1, wherein the list of entriesincludes primary entries comprising one or more of: decrease respiratoryrate; decrease inspiratory time; increase flow; adjust ventilatorysettings until end-expiratory flow (EEF) approximates zero; investigatereasons for increased resistance; and investigate reasons for increasedcompliance.
 3. The ventilator-implemented method of claim 2, wherein thelist of entries further includes secondary entries, comprising one ormore of: decrease tidal volume (V_(T)); and change to a square flowwaveform.
 4. The ventilator-implemented method of claim 2, wherein thesecondary entries comprise: decrease inspiratory pressure in order todecrease delivered tidal volume (V_(T)) so that expiratory time (T_(E))is adequate to completely exhale delivered V_(T).
 5. Theventilator-implemented method of claim 1, wherein the ventilatory dataincludes expiratory flow data, the method further comprising: receivingone or more predetermined thresholds associated with end-expiratory flow(EEF); detecting that EEF is positive when the EEF breaches the one ormore predetermined thresholds; and determining that Auto-PEEP isimplicated for the non-triggering patient when EEF is positive for apredetermined number of breaths.
 6. The ventilator-implemented method ofclaim 1, wherein the ventilatory data includes respiratory resistancedata and respiratory compliance data, the method further comprising:calculating a time required to reach functional residual capacity (FRC);comparing the time required to reach FRC with expiratory time (T_(E));and determining that Auto-PEEP is implicated for the non-triggeringpatient when the time required to reach FRC is greater than T_(E). 7.The ventilator-implemented method of claim 1, wherein the ventilatorydata includes pressure data, the method further comprising: receiving apositive end-expiratory pressure (PEEP) setting, wherein the PEEPsetting is about 0 cm H₂O or greater; receiving one or morepredetermined thresholds associated with end-expiratory pressure (EEP);detecting that the EEP breaches the one or more predetermined thresholdswhen the EEP minus the PEEP setting is greater than the one or morepredetermined thresholds; and determining that Auto-PEEP is implicatedfor the non-triggering patient when the EEP breaches the one or morepredetermined thresholds.
 8. The ventilator-implemented method of claim1, wherein the ventilatory data includes respiratory resistance data,the method further comprising: receiving one or more predeterminedthresholds associated with the respiratory resistance data; detectingthat respiratory resistance has increased when the respiratoryresistance data breaches the one or more predetermined thresholds; anddetermining that Auto-PEEP is implicated for the non-triggering patientwhen the respiratory resistance has increased.
 9. Theventilator-implemented method of claim 1, wherein the ventilatory dataincludes a pulmonary time constant and an expiratory time (T_(E)), andthe method further comprising: comparing the pulmonary time constant tothe T_(E); and determining that Auto-PEEP is implicated for thenon-triggering patient when the T_(E) is less than three pulmonary timeconstants.
 10. A ventilatory system for issuing a prompt when Auto-PEEPis implicated during ventilation of a non-triggering patient,comprising: at least one processor; and at least one memory,communicatively coupled to the at least one processor and containinginstructions that, when executed by the at least one processor, cause acontroller to: receive one or more ventilatory settings associated withventilation of the non-triggering patient; detect that Auto-PEEP isimplicated for the non-triggering patient upon detecting that parameterdata breaches one or more predetermined thresholds, wherein the one ormore predetermined thresholds are based at least in part on the one ormore ventilatory settings; determine a list of entries for mitigatingAuto-PEEP based at least in part on identifying the patient asnon-triggering, wherein at least one entry of the list of entries isdifferent for the non-triggering patient than for a triggering patient;and issue a prompt when Auto-PEEP is implicated, the prompt displaying:a notification that Auto-PEEP is implicated; and a list of entries formitigating Auto-PEEP.
 11. The ventilatory system of claim 10, furthercomprising: determine the notification based at least in part on theparameter data that implicated Auto-PEEP.
 12. The ventilatory system ofclaim 11, wherein the notification-comprises information regarding theparameter data that implicated Auto-PEEP.
 13. The ventilatory system ofclaim 10, wherein the list of entries for mitigating Auto-PEEP are basedat least in part on evaluating the parameter data that implicatedAuto-PEEP.
 14. The ventilatory system of claim 10, wherein the list ofentries comprises primary entries comprising one or more of: decreaserespiratory rate; decrease inspiratory time; increase flow; adjustventilatory settings until end-expiratory flow (EEF) approximates zero;investigate reasons for increased resistance; and investigate reasonsfor increased compliance.
 15. The ventilatory system of claim 14,wherein the list of entries includes one or more secondary entries, theone or more secondary entries comprising increasing expiratory time(T_(E)) by one or more of: decreasing tidal volume (V_(T)); and changingto a square flow waveform.
 16. The ventilatory system of claim 14,wherein the list of entries includes one or more secondary entries, theone or more secondary entries comprising: decrease inspiratory pressurein order to decrease delivered tidal volume (V_(T)) so that expiratorytime (T_(E)) is adequate to completely exhale delivered V_(T).
 17. Aventilator-implemented method for detecting Auto-PEEP during ventilationof a non-triggering patient, the method implemented on a ventilatorhaving at least one processor, the method comprising: collecting dataassociated with ventilatory parameters; determining one or morepredetermined thresholds for detecting Auto-PEEP; and determining, bythe at least one processor, that Auto-PEEP is implicated for thenon-triggering patient upon detecting that the ventilatory parameterdata breaches the one or more predetermined thresholds; determining alist of entries for mitigating Auto-PEEP based at least in part onidentifying the patient as non-triggering, wherein at least one entry ofthe list of entries is different for the non-triggering patient than fora triggering patient; and issuing a prompt when Auto-PEEP is implicated,the prompt displaying: a notification that Auto-PEEP is implicated; andthe list of entries for mitigating Auto-PEEP.
 18. Theventilator-implemented method of claim 17, wherein the list of entriesincludes primary entries comprising one or more of: decrease respiratoryrate; decrease inspiratory time; increase flow; adjust ventilatorysettings until end-expiratory flow (EEF) approximates zero; investigatereasons for increased resistance; and investigate reasons for increasedcompliance.
 19. The ventilator-implemented method of claim 18, whereinthe list of entries further includes one or more secondary entries, theone or more secondary entries comprising increasing expiratory time(T_(E)) by one or more of: decreasing tidal volume (V_(T)); and changingto a square flow waveform.
 20. The ventilator-implemented method ofclaim 18, wherein the list of entries further includes one or moresecondary entries, the one or more secondary entries comprising:decrease inspiratory pressure in order to decrease delivered tidalvolume (V_(T)) so that expiratory time (T_(E)) is adequate to completelyexhale delivered V_(T).